Refactored DB Forge

- PDO subdrivers are isolated from each other now.
- Added compatibility for pretty much all of the features, for every DB platform.
- Unified the way that stuff works in general.
- Fixes issue #1005.

31 files changed, 3487 insertions, 1387 deletions

diff --git a/system/core/Loader.php b/system/core/Loader.php
index 88fbdb6e1..808fa80df 100644
--- a/system/core/Loader.php
+++ b/system/core/Loader.php
@@ -392,7 +392,20 @@ class CI_Loader {
 
 		require_once(BASEPATH.'database/DB_forge.php');
 		require_once(BASEPATH.'database/drivers/'.$CI->db->dbdriver.'/'.$CI->db->dbdriver.'_forge.php');
-		$class = 'CI_DB_'.$CI->db->dbdriver.'_forge';
+
+		if ( ! empty($CI->db->subdriver))
+		{
+			$driver_path = BASEPATH.'database/drivers/'.$CI->db->dbdriver.'/subdrivers/'.$CI->db->dbdriver.'_'.$CI->db->subdriver.'_forge.php';
+			if (file_exists($driver_path))
+			{
+				require_once($driver_path);
+				$class = 'CI_DB_'.$CI->db->dbdriver.'_'.$CI->db->subdriver.'_forge';
+			}
+		}
+		else
+		{
+			$class = 'CI_DB_'.$CI->db->dbdriver.'_forge';
+		}
 
 		$CI->dbforge = new $class();
 	}
diff --git a/system/database/DB_forge.php b/system/database/DB_forge.php
index f46237e25..d8ecefe77 100644
--- a/system/database/DB_forge.php
+++ b/system/database/DB_forge.php
@@ -36,6 +36,13 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 abstract class CI_DB_forge {
 
 	/**
+	 * Database object
+	 *
+	 * @var	object
+	 */
+	public $db;
+
+	/**
 	 * Fields data
 	 *
 	 * @var	array
@@ -80,23 +87,68 @@ abstract class CI_DB_forge {
 	protected $_drop_database	= 'DROP DATABASE %s';
 
 	/**
-	 * DROP TABLE statement
+	 * CREATE TABLE statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table	= "%s %s (%s\n)";
+
+	/**
+	 * CREATE TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table_if	= 'CREATE TABLE IF NOT EXISTS';
+
+	/**
+	 * CREATE TABLE keys flag
+	 *
+	 * Whether table keys are created from within the
+	 * CREATE TABLE statement.
+	 *
+	 * @var	bool
+	 */
+	protected $_create_table_keys	= FALSE;
+
+	/**
+	 * DROP TABLE IF EXISTS statement
 	 *
 	 * @var	string
 	 */
-	protected $_drop_table		= 'DROP TABLE IF EXISTS %s';
+	protected $_drop_table_if	= 'DROP TABLE IF EXISTS';
 
 	/**
 	 * RENAME TABLE statement
 	 *
 	 * @var	string
 	 */
-	protected $_rename_table	= 'ALTER TABLE %s RENAME TO %s';
+	protected $_rename_table	= 'ALTER TABLE %s RENAME TO %s;';
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	bool|array
+	 */
+	protected $_unsigned		= TRUE;
+
+	/**
+	 * NULL value representatin in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= '';
+
+	/**
+	 * DEFAULT value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_default		= ' DEFAULT ';
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Constructor
+	 * Class constructor
 	 *
 	 * @return	void
 	 */
@@ -113,7 +165,7 @@ abstract class CI_DB_forge {
 	/**
 	 * Create database
 	 *
-	 * @param	string	the database name
+	 * @param	string	$db_name
 	 * @return	bool
 	 */
 	public function create_database($db_name)
@@ -140,7 +192,7 @@ abstract class CI_DB_forge {
 	/**
 	 * Drop database
 	 *
-	 * @param	string	the database name
+	 * @param	string	$db_name
 	 * @return	bool
 	 */
 	public function drop_database($db_name)
@@ -176,25 +228,25 @@ abstract class CI_DB_forge {
 	/**
 	 * Add Key
 	 *
-	 * @param	string	key
-	 * @param	string	type
+	 * @param	string	$key
+	 * @param	bool	$primary
 	 * @return	object
 	 */
 	public function add_key($key = '', $primary = FALSE)
 	{
-		if ($primary && is_array($key))
+		if (empty($key))
+		{
+			show_error('Key information is required for that operation.');
+		}
+
+		if (is_array($key))
 		{
 			foreach ($key as $one)
 			{
 				$this->add_key($one, $primary);
 			}
 
-			return;
-		}
-
-		if ($key === '')
-		{
-			show_error('Key information is required for that operation.');
+			return $this;
 		}
 
 		if ($primary === TRUE)
@@ -214,12 +266,12 @@ abstract class CI_DB_forge {
 	/**
 	 * Add Field
 	 *
-	 * @param	string	collation
+	 * @param	array	$field
 	 * @return	object
 	 */
 	public function add_field($field = '')
 	{
-		if ($field === '')
+		if (empty($field))
 		{
 			show_error('Field information is required.');
 		}
@@ -261,8 +313,8 @@ abstract class CI_DB_forge {
 	/**
 	 * Create Table
 	 *
-	 * @param	string	$table = ''
-	 * @param	bool	$if_not_exists = FALSE
+	 * @param	string	$table		Table name
+	 * @param	bool	$if_not_exists	Whether to add IF NOT EXISTS condition
 	 * @return	bool
 	 */
 	public function create_table($table = '', $if_not_exists = FALSE)
@@ -271,51 +323,129 @@ abstract class CI_DB_forge {
 		{
 			show_error('A table name is required for that operation.');
 		}
+		else
+		{
+			$table = $this->db->dbprefix.$table;
+		}
 
 		if (count($this->fields) === 0)
 		{
 			show_error('Field information is required.');
 		}
 
-		$sql = $this->_create_table($this->db->dbprefix.$table, $this->fields, $this->primary_keys, $this->keys, $if_not_exists);
-		$this->_reset();
+		$sql = $this->_create_table($table, $if_not_exists);
 
 		if (is_bool($sql))
 		{
-			return $sql;
+			$this->_reset();
+			if ($sql === FALSE)
+			{
+				return ($this->db->db_debug) ? $this->db->display_error('db_unsuported_feature') : FALSE;
+			}
 		}
 
-		if (($result = $this->db->query($sql)) !== FALSE && ! empty($this->db->data_cache['table_names']))
+		if (($result = $this->db->query($sql)) !== FALSE)
 		{
-			$this->db->data_cache['table_names'][] = $this->db->dbprefix.$table;
+			empty($this->db->data_cache['table_names']) OR $this->db->data_cache['table_names'][] = $table;
+
+			// Most databases don't support creating indexes from within the CREATE TABLE statement
+			if ( ! empty($this->keys))
+			{
+				for ($i = 0, $sqls = $this->_process_indexes($table), $c = count($sqls); $i < $c; $i++)
+				{
+					$this->db->query($sqls[$i]);
+				}
+			}
 		}
 
+		$this->_reset();
 		return $result;
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
+	 * Create Table
+	 *
+	 * @param	string	$table		Table name
+	 * @param	bool	$if_not_exists	Whether to add 'IF NOT EXISTS' condition
+	 * @return	mixed
+	 */
+	protected function _create_table($table, $if_not_exists)
+	{
+		if ($if_not_exists === TRUE && $this->_create_table_if === FALSE)
+		{
+			if ($this->db->table_exists($table))
+			{
+				return TRUE;
+			}
+			else
+			{
+				$if_not_exists = FALSE;
+			}
+		}
+
+		$sql = ($if_not_exists)
+			? sprintf($this->_create_table_if, $this->db->escape_identifiers($table))
+			: 'CREATE TABLE';
+
+		$columns = $this->_process_fields(TRUE);
+		for ($i = 0, $c = count($columns); $i < $c; $i++)
+		{
+			$columns[$i] = ($columns[$i]['_literal'] !== FALSE)
+					? "\n\t".$columns[$i]['_literal']
+					: "\n\t".$this->_process_column($columns[$i]);
+		}
+
+		$columns = implode(',', $columns)
+				.$this->_process_primary_keys($table);
+
+		// Are indexes created from within the CREATE TABLE statement? (e.g. in MySQL)
+		if ($this->_create_table_keys === TRUE)
+		{
+			$columns .= $this->_process_indexes();
+		}
+
+		// _create_table will usually have the following format: "%s %s (%s\n)"
+		$sql = sprintf($this->_create_table.';',
+			$sql,
+			$this->db->escape_identifiers($table),
+			$columns
+		);
+
+		return $sql;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Drop Table
 	 *
-	 * @param	string	the table name
+	 * @param	string	$table_name	Table name
+	 * @param	bool	$if_exists	Whether to add an IF EXISTS condition
 	 * @return	bool
 	 */
-	public function drop_table($table_name)
+	public function drop_table($table_name, $if_exists = FALSE)
 	{
 		if ($table_name === '')
 		{
 			return ($this->db->db_debug) ? $this->db->display_error('db_table_name_required') : FALSE;
 		}
-		elseif ($this->_drop_table === FALSE)
+
+		$query = $this->_drop_table($this->db->dbprefix.$table_name, $if_exists);
+		if ($query === FALSE)
 		{
 			return ($this->db->db_debug) ? $this->db->display_error('db_unsuported_feature') : FALSE;
 		}
+		elseif ($query === TRUE)
+		{
+			return TRUE;
+		}
 
-		$result = $this->db->query(sprintf($this->_drop_table, $this->db->escape_identifiers($this->db->dbprefix.$table_name)));
+		$query = $this->db->query($query);
 
 		// Update table list cache
-		if ($result && ! empty($this->db->data_cache['table_names']))
+		if ($query && ! empty($this->db->data_cache['table_names']))
 		{
 			$key = array_search(strtolower($this->db->dbprefix.$table_name), array_map('strtolower', $this->db->data_cache['table_names']), TRUE);
 			if ($key !== FALSE)
@@ -324,7 +454,40 @@ abstract class CI_DB_forge {
 			}
 		}
 
-		return $result;
+		return $query;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Drop Table
+	 *
+	 * Generates a platform-specific DROP TABLE string
+	 *
+	 * @param	string	$table		Table name
+	 * @param	bool	$if_exists	Whether to add an IF EXISTS condition
+	 * @return	string
+	 */
+	protected function _drop_table($table, $if_exists)
+	{
+		$sql = 'DROP TABLE';
+
+		if ($if_exists)
+		{
+			if ($this->_drop_table_if === FALSE)
+			{
+				if ( ! $this->db->table_exists($table))
+				{
+					return TRUE;
+				}
+			}
+			else
+			{
+				$sql = sprintf($this->_drop_table_if, $this->db->escape_identifiers($table));
+			}
+		}
+
+		return $sql.' '.$this->db->escape_identifiers($table);
 	}
 
 	// --------------------------------------------------------------------
@@ -332,8 +495,8 @@ abstract class CI_DB_forge {
 	/**
 	 * Rename Table
 	 *
-	 * @param	string	the old table name
-	 * @param	string	the new table name
+	 * @param	string	$table_name	Old table name
+	 * @param	string	$new_table_name	New table name
 	 * @return	bool
 	 */
 	public function rename_table($table_name, $new_table_name)
@@ -370,32 +533,37 @@ abstract class CI_DB_forge {
 	/**
 	 * Column Add
 	 *
-	 * @param	string	the table name
-	 * @param	string	the column name
-	 * @param	string	the column definition
+	 * @param	string	$table	Table name
+	 * @param	array	$field	Column definition
 	 * @return	bool
 	 */
-	public function add_column($table = '', $field = array(), $after_field = '')
+	public function add_column($table = '', $field = array())
 	{
 		if ($table === '')
 		{
 			show_error('A table name is required for that operation.');
 		}
 
-		// add field info into field array, but we can only do one at a time
-		// so we cycle through
+		// Work-around for literal column definitions
+		if ( ! is_array($field))
+		{
+			$field = array($field);
+		}
+
 		foreach (array_keys($field) as $k)
 		{
 			$this->add_field(array($k => $field[$k]));
+		}
 
-			if (count($this->fields) === 0)
-			{
-				show_error('Field information is required.');
-			}
-
-			$sql = $this->_alter_table('ADD', $this->db->dbprefix.$table, $this->fields, $after_field);
-			$this->_reset();
+		$sqls = $this->_alter_table('ADD', $this->db->dbprefix.$table, $this->_process_fields());
+		$this->_reset();
+		if ($sqls === FALSE)
+		{
+			return ($this->db->db_debug) ? $this->db->display_error('db_unsuported_feature') : FALSE;
+		}
 
+		for ($i = 0, $c = count($sqls); $i < $c; $i++)
+		{
 			if ($this->db->query($sql) === FALSE)
 			{
 				return FALSE;
@@ -410,8 +578,8 @@ abstract class CI_DB_forge {
 	/**
 	 * Column Drop
 	 *
-	 * @param	string	the table name
-	 * @param	string	the column name
+	 * @param	string	$table		Table name
+	 * @param	string	$column_name	Column name
 	 * @return	bool
 	 */
 	public function drop_column($table = '', $column_name = '')
@@ -426,7 +594,13 @@ abstract class CI_DB_forge {
 			show_error('A column name is required for that operation.');
 		}
 
-		return $this->db->query($this->_alter_table('DROP', $this->db->dbprefix.$table, $column_name));
+		$sql = $this->_alter_table('DROP', $this->db->dbprefix.$table, $column_name);
+		if ($sql === FALSE)
+		{
+			return ($this->db->db_debug) ? $this->db->display_error('db_unsuported_feature') : FALSE;
+		}
+
+		return $this->db->query($sql);
 	}
 
 	// --------------------------------------------------------------------
@@ -434,8 +608,8 @@ abstract class CI_DB_forge {
 	/**
 	 * Column Modify
 	 *
-	 * @param	string	$table = ''
-	 * @param	string	$field = array()	column definition
+	 * @param	string	$table	Table name
+	 * @param	string	$field	Column definition
 	 * @return	bool
 	 */
 	public function modify_column($table = '', $field = array())
@@ -445,32 +619,363 @@ abstract class CI_DB_forge {
 			show_error('A table name is required for that operation.');
 		}
 
-		// add field info into field array, but we can only do one at a time
-		// so we cycle through
+		// Work-around for literal column definitions
+		if ( ! is_array($field))
+		{
+			$field = array($field);
+		}
+
 		foreach (array_keys($field) as $k)
 		{
-			// If no name provided, use the current name
-			if ( ! isset($field[$k]['name']))
+			$this->add_field(array($k => $field[$k]));
+		}
+
+		if (count($this->fields) === 0)
+		{
+			show_error('Field information is required.');
+		}
+
+		$sqls = $this->_alter_table('CHANGE', $this->db->dbprefix.$table, $this->fields);
+		$this->_reset();
+		if ($sqls === FALSE)
+		{
+			return ($this->db->db_debug) ? $this->db->display_error('db_unsuported_feature') : FALSE;
+		}
+
+		for ($i = 0, $c = count($sqls); $i < $c; $i++)
+		{
+			if ($this->db->query($sql) === FALSE)
 			{
-				$field[$k]['name'] = $k;
+				return FALSE;
 			}
+		}
 
-			$this->add_field(array($k => $field[$k]));
-			if (count($this->fields) === 0)
+		return TRUE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' ';
+
+		// DROP has everything it needs now.
+		if ($alter_type === 'DROP')
+		{
+			return $sql.'DROP COLUMN '.$this->db->escape_identifiers($field);
+		}
+
+		$sqls = array();
+		for ($i = 0, $c = count($field), $sql .= $alter_type.' COLUMN '; $i < $c; $i++)
+		{
+			$sqls[] = $sql
+				.($field[$i]['_literal'] !== FALSE ? $field[$i]['_literal'] : $this->_process_column($field[$i]));
+		}
+
+		return $sqls;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process fields
+	 *
+	 * @param	bool	$create_table
+	 * @return	array
+	 */
+	protected function _process_fields($create_table = FALSE)
+	{
+		$fields = array();
+
+		foreach ($this->fields as $key => $attributes)
+		{
+			if (is_int($key) && ! is_array($attributes))
 			{
-				show_error('Field information is required.');
+				$fields[] = array('_literal' => $attributes);
+				continue;
 			}
 
-			$sql = $this->_alter_table('CHANGE', $this->db->dbprefix.$table, $this->fields);
-			$this->_reset();
+			$attributes = array_change_key_case($attributes, CASE_UPPER);
 
-			if ($this->db->query($sql) === FALSE)
+			if ($create_table === TRUE && empty($attributes['TYPE']))
 			{
-				return FALSE;
+				continue;
+			}
+
+			if (isset($attributes['TYPE']))
+			{
+				$this->_attr_type($attributes);
+				$this->_attr_unsigned($attributes, $field);
 			}
+
+			$field = array(
+					'name'			=> $key,
+					'new_name'		=> isset($attributes['NAME']) ? $attributes['NAME'] : NULL,
+					'type'			=> isset($attributes['TYPE']) ? $attributes['TYPE'] : NULL,
+					'length'		=> '',
+					'unsigned'		=> '',
+					'null'			=> '',
+					'unique'		=> '',
+					'default'		=> '',
+					'auto_increment'	=> '',
+					'_literal'		=> FALSE
+			);
+
+			$this->_attr_default($attributes, $field);
+
+			if (isset($attributes['NULL']))
+			{
+				if ($attributes['NULL'] === TRUE)
+				{
+					$field['null'] = empty($this->_null) ? '' : ' '.$this->_null;
+				}
+				elseif ($create_table === TRUE)
+				{
+					$field['null'] = ' NOT NULL';
+				}
+			}
+
+			$this->_attr_auto_increment($attributes, $field);
+			$this->_attr_unique($attributes, $field);
+
+			if (isset($attributes['TYPE']) && ! empty($attributes['CONSTRAINT']))
+			{
+				switch (strtoupper($attributes['TYPE']))
+				{
+					case 'ENUM':
+					case 'SET':
+						$attributes['CONSTRAINT'] = $this->db->escape($attributes['CONSTRAINT']);
+					default:
+						$field['length'] = is_array($attributes['CONSTRAINT'])
+								? '('.implode(',', $attributes['CONSTRAINT']).')'
+								: '('.$attributes['CONSTRAINT'].')';
+						break;
+				}
+			}
+
+			$fields[] = $field;
 		}
 
-		return TRUE;
+		return $fields;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process column
+	 *
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.' '.$field['type'].$field['length']
+			.$field['unsigned']
+			.$field['default']
+			.$field['null']
+			.$field['auto_increment']
+			.$field['unique'];
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		// Usually overriden by drivers
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute UNSIGNED
+	 *
+	 * Depending on the _unsigned property value:
+	 *
+	 *	- TRUE will always set $field['unsigned'] to 'UNSIGNED'
+	 *	- FALSE will always set $field['unsigned'] to ''
+	 *	- array(TYPE) will set $field['unsigned'] to 'UNSIGNED',
+	 *		if $attributes['TYPE'] is found in the array
+	 *	- array(TYPE => UTYPE) will change $field['type'],
+	 *		from TYPE to UTYPE in case of a match
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_unsigned(&$attributes, &$field)
+	{
+		if (empty($attributes['UNSIGNED']) OR $attributes['UNSIGNED'] !== TRUE)
+		{
+			return;
+		}
+
+		// Reset the attribute in order to avoid issues if we do type conversion
+		$attributes['UNSIGNED'] = FALSE;
+
+		if (is_array($this->_unsigned))
+		{
+			foreach (array_keys($this->_unsigned) as $key)
+			{
+				if (is_int($key) && strcasecmp($attributes['TYPE'], $this->_unsigned[$key]) === 0)
+				{
+					$field['unsigned'] = ' UNSIGNED';
+					return;
+				}
+				elseif (is_string($key) && strcasecmp($attributes['TYPE'], $key) === 0)
+				{
+					$field['type'] = $key;
+					return;
+				}
+			}
+
+			return;
+		}
+
+		$field['unsigned'] = ($this->_unsigned === TRUE) ? ' UNSIGNED' : '';
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute DEFAULT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_default(&$attributes, &$field)
+	{
+		if ($this->_default === FALSE)
+		{
+			return;
+		}
+
+		if (array_key_exists('DEFAULT', $attributes))
+		{
+			if ($attributes['DEFAULT'] === NULL)
+			{
+				$field['default'] = empty($this->_null) ? '' : $this->_default.$this->_null;
+
+				// Override the NULL attribute if that's our default
+				$attributes['NULL'] = NULL;
+				$field['null'] = empty($this->_null) ? '' : ' '.$this->_null;
+			}
+			else
+			{
+				$field['default'] = $this->_default.$this->db->escape($attributes['DEFAULT']);
+			}
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute UNIQUE
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_unique(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['UNIQUE']) && $attributes['UNIQUE'] === TRUE)
+		{
+			$field['unique'] = ' UNIQUE';
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE)
+		{
+			$field['auto_increment'] = ' AUTO_INCREMENT';
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process primary keys
+	 *
+	 * @param	string	$table	Table name
+	 * @return	string
+	 */
+	protected function _process_primary_keys($table)
+	{
+		$sql = '';
+
+		for ($i = 0, $c = count($this->primary_keys); $i < $c; $i++)
+		{
+			if ( ! isset($this->fields[$this->primary_keys[$i]]))
+			{
+				unset($this->primary_keys[$i]);
+			}
+		}
+
+		if (count($this->primary_keys) > 0)
+		{
+			$sql .= ",\n\tCONSTRAINT ".$this->db->escape_identifiers('pk_'.$table)
+				.' PRIMARY KEY('.implode(', ', $this->db->escape_identifiers($this->primary_keys)).')';
+		}
+
+		return $sql;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process indexes
+	 *
+	 * @param	string	$table
+	 * @return	string
+	 */
+	protected function _process_indexes($table = NULL)
+	{
+		$table = $this->db->escape_identifiers($table);
+		$sqls = array();
+
+		for ($i = 0, $c = count($this->keys); $i < $c; $i++)
+		{
+			if ( ! isset($this->fields[$this->keys[$i]]))
+			{
+				unset($this->keys[$i]);
+				continue;
+			}
+
+			is_array($this->keys[$i]) OR $this->keys[$i] = array($this->keys[$i]);
+
+			$sqls[] = 'CREATE INDEX '.$this->db->escape_identifiers(implode('_', $this->keys[$i]))
+				.' ON '.$this->db->escape_identifiers($table)
+				.' ('.implode(', ', $this->db->escape_identifiers($this->keys[$i])).');';
+		}
+
+		return $sqls;
 	}
 
 	// --------------------------------------------------------------------
diff --git a/system/database/drivers/cubrid/cubrid_forge.php b/system/database/drivers/cubrid/cubrid_forge.php
index 33d502137..e3f8bc334 100644
--- a/system/database/drivers/cubrid/cubrid_forge.php
+++ b/system/database/drivers/cubrid/cubrid_forge.php
@@ -42,8 +42,6 @@ class CI_DB_cubrid_forge extends CI_DB_forge {
 	 */
 	protected $_create_database	= FALSE;
 
-	// --------------------------------------------------------------------
-
 	/**
 	 * DROP DATABASE statement
 	 *
@@ -52,177 +50,121 @@ class CI_DB_cubrid_forge extends CI_DB_forge {
 	protected $_drop_database	= FALSE;
 
 	/**
-	 * Process Fields
+	 * CREATE TABLE IF statement
 	 *
-	 * @param	mixed	$fields
-	 * @return	string
+	 * @var	string
+	 */
+	protected $_create_table_if	= FALSE;
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
 	 */
-	protected function _process_fields($fields)
+	protected $_unsigned		= array(
+		'SHORT'		=> 'INTEGER',
+		'SMALLINT'	=> 'INTEGER',
+		'INT'		=> 'BIGINT',
+		'INTEGER'	=> 'BIGINT',
+		'BIGINT'	=> 'NUMERIC',
+		'FLOAT'		=> 'DOUBLE',
+		'REAL'		=> 'DOUBLE'
+	);
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
 	{
-		$current_field_count = 0;
-		$sql = '';
+		if (in_array($alter_type, array('DROP', 'ADD'), TRUE))
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
 
-		foreach ($fields as $field => $attributes)
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		$sqls = array();
+		for ($i = 0, $c = count($field); $i < $c; $i++)
 		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
+			if ($field[$i]['_literal'] !== FALSE)
 			{
-				$sql .= "\n\t".$attributes;
+				$sqls[] = $sql.' CHANGE '.$field[$i]['_literal'];
 			}
 			else
 			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field);
-
-				empty($attributes['NAME']) OR $sql .= ' '.$this->db->escape_identifiers($attributes['NAME']).' ';
-
-				if ( ! empty($attributes['TYPE']))
-				{
-					$sql .= ' '.$attributes['TYPE'];
-
-					if ( ! empty($attributes['CONSTRAINT']))
-					{
-						switch (strtolower($attributes['TYPE']))
-						{
-							case 'decimal':
-							case 'float':
-							case 'numeric':
-								$sql .= '('.implode(',', $attributes['CONSTRAINT']).')';
-								break;
-							case 'enum':
-								// Will be supported in the future as part a part of
-								// MySQL compatibility features.
-								break;
-							case 'set':
-								$sql .= '("'.implode('","', $attributes['CONSTRAINT']).'")';
-								break;
-							default:
-								$sql .= '('.$attributes['CONSTRAINT'].')';
-						}
-					}
-				}
-
-			/* As of version 8.4.1 CUBRID does not support UNSIGNED INTEGER data type.
-			 * Will be supported in the next release as a part of MySQL Compatibility.
-			 *
-				if (isset($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-			 */
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
-
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
-
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
-
-				if ( ! empty($attributes['UNIQUE']) && $attributes['UNIQUE'] === TRUE)
+				$sqls[] = $sql.' CHANGE '.$this->_process_column($field[$i]);
+				if ( ! empty($field[$i]['new_name']))
 				{
-					$sql .= ' UNIQUE';
+					$sqls[] = $sql.' RENAME COLUMN '.$this->db->escape_identifiers($field[$i]['name'])
+						.' AS '.$this->db->escape_identifiers($field[$i]['name']);
 				}
 			}
-
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
-			}
 		}
 
-		return $sql;
+		return $sqls;
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Create Table
+	 * Field attribute TYPE
 	 *
-	 * @param	string	the table name
-	 * @param	mixed	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	bool
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
+	protected function _attr_type(&$attributes)
 	{
-		$sql = 'CREATE TABLE ';
-
-		/* As of version 8.4.1 CUBRID does not support this SQL syntax.
-		if ($if_not_exists === TRUE)
+		switch (strtoupper($attributes['TYPE']))
 		{
-			$sql .= 'IF NOT EXISTS ';
+			case 'TINYINT':
+				$attributes['TYPE'] = 'SMALLINT';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			default: return;
 		}
-		*/
-
-		$sql .= $this->db->escape_identifiers($table).' ('.$this->_process_fields($fields);
-
-		// If there is a PK defined
-		if (count($primary_keys) > 0)
-		{
-			$key_name = $this->db->escape_identifiers('pk_'.$table.'_'.implode('_', $primary_keys));
-			$sql .= ",\n\tCONSTRAINT ".$key_name.' PRIMARY KEY('.implode(', ', $this->db->escape_identifiers($primary_keys)).')';
-		}
-
-		if (is_array($keys) && count($keys) > 0)
-		{
-			foreach ($keys as $key)
-			{
-				if (is_array($key))
-				{
-					$key_name = $this->db->escape_identifiers('idx_'.$table.implode('_', $key));
-					$key = $this->db->escape_identifiers($key);
-				}
-				else
-				{
-					$key_name = $this->db->escape_identifiers('idx_'.$table.$key);
-					$key = array($key_name);
-				}
-
-				$sql .= ",\n\tKEY ".$key_name.' ('.implode(', ', $key).')';
-			}
-		}
-
-		return $sql."\n);";
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
-	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
+	 * Process indexes
 	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	array	fields
-	 * @param	string	the field after which we should add the new field
+	 * @param	string	$table	(ignored)
 	 * @return	string
 	 */
-	protected function _alter_table($alter_type, $table, $fields, $after_field = '')
+	protected function _process_indexes($table = NULL)
 	{
-		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' ';
+		$sql = '';
 
-		// DROP has everything it needs now.
-		if ($alter_type === 'DROP')
+		for ($i = 0, $c = count($this->keys); $i < $c; $i++)
 		{
-			return $sql.$this->db->escape_identifiers($fields);
+			if ( ! isset($this->fields[$this->keys[$i]]))
+			{
+				unset($this->keys[$i]);
+				continue;
+			}
+
+			is_array($this->keys[$i]) OR $this->keys[$i] = array($this->keys[$i]);
+
+			$sql .= ",\n\tKEY ".$this->db->escape_identifiers(implode('_', $this->keys[$i]))
+				.' ('.implode(', ', $this->db->escape_identifiers($this->keys[$i])).')';
 		}
 
-		return $sql.$this->_process_fields($fields)
-			.($after_field !== '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
+		$this->keys = array();
+
+		return $sql;
 	}
 
 }
diff --git a/system/database/drivers/ibase/ibase_forge.php b/system/database/drivers/ibase/ibase_forge.php
index 7c4d00a23..a0c4e6563 100644
--- a/system/database/drivers/ibase/ibase_forge.php
+++ b/system/database/drivers/ibase/ibase_forge.php
@@ -36,11 +36,43 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 class CI_DB_ibase_forge extends CI_DB_forge {
 
 	/**
-	 * DROP TABLE statement
+	 * CREATE TABLE IF statement
 	 *
 	 * @var	string
 	 */
-	protected $_drop_table	= 'DROP TABLE %s';
+	protected $_create_table_if	= FALSE;
+
+	/**
+	 * RENAME TABLE statement
+	 *
+	 * @var	string
+	 */
+	protected $_rename_table	= FALSE;
+
+	/**
+	 * DROP TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_table_if	= FALSE;
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'SMALLINT'	=> 'INTEGER',
+		'INTEGER'	=> 'INT64',
+		'FLOAT'		=> 'DOUBLE PRECISION'
+	);
+
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= 'NULL';
 
 	// --------------------------------------------------------------------
 
@@ -65,8 +97,7 @@ class CI_DB_ibase_forge extends CI_DB_forge {
 	/**
 	 * Drop database
 	 *
-	 * @param	string	the database name
-	 *		- not used in this driver, the current db is dropped
+	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
 	public function drop_database($db_name = '')
@@ -90,110 +121,119 @@ class CI_DB_ibase_forge extends CI_DB_forge {
 	// --------------------------------------------------------------------
 
 	/**
-	 * Create Table
+	 * ALTER TABLE
 	 *
-	 * @param	string	the table name
-	 * @param	array	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	string
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
-	{
-		$sql = 'CREATE TABLE ';
-
-		$sql .= $this->db->escape_identifiers($table).'(';
-		$current_field_count = 0;
+	protected function _alter_table($alter_type, $table, $field)
+ 	{
+		if (in_array($alter_type, array('DROP', 'ADD'), TRUE))
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
 
-		foreach ($fields as $field => $attributes)
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		$sqls = array();
+		for ($i = 0, $c = count($field), $sql .= $alter_type.' '; $i < $c; $i++)
 		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
+			if ($field[$i]['_literal'] !== FALSE)
 			{
-				$sql .= "\n\t".$attributes;
+				return FALSE;
 			}
-			else
-			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field).' '.$attributes['TYPE'];
-
-				empty($attributes['CONSTRAINT']) OR $sql .= '('.$attributes['CONSTRAINT'].')';
-
-				if ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
 
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
-
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
+			if (isset($field[$i]['type']))
+			{
+				$sqls[] = $sql.' TYPE '.$field[$i]['type'].$field[$i]['length'];
 			}
 
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
+			if ( ! empty($field[$i]['default']))
 			{
-				$sql .= ',';
+				$sqls[] = $sql.' ALTER '.$this->db->escape_identifiers($field[$i]['name'])
+					.' SET '.$field[$i]['default'];
 			}
-		}
 
-		if (count($primary_keys) > 0)
-		{
-			$primary_keys = $this->db->escape_identifiers($primary_keys);
-			$sql .= ",\n\tPRIMARY KEY (".implode(', ', $primary_keys).')';
-		}
-
-		if (is_array($keys) && count($keys) > 0)
-		{
-			foreach ($keys as $key)
+			if (isset($field[$i]['null']))
 			{
-				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
-					: array($this->db->escape_identifiers($key));
+				$sqls[] = 'UPDATE "RDB$RELATION_FIELDS" SET "RDB$NULL_FLAG" = '
+					.($field[$i]['null'] === TRUE ? 'NULL' : '1')
+					.' WHERE "RDB$FIELD_NAME" = '.$this->db->escape($field[$i]['name'])
+					.' AND "RDB$RELATION_NAME" = '.$this->db->escape($table);
+			}
 
-				$sql .= ",\n\tUNIQUE (".implode(', ', $key).')';
+			if ( ! empty($field[$i]['new_name']))
+			{
+				$sqls[] = $sql.' ALTER '.$this->db->escape_identifiers($field[$i]['name'])
+					.' TO '.$this->db->escape_identifiers($field[$i]['new_name']);
 			}
 		}
 
-		return $sql."\n)";
+		return $sqls;
+ 	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process column
+	 *
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.' '.$field['type'].$field['length']
+			.$field['null']
+			.$field['unique']
+			.$field['default'];
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
+	 * Field attribute TYPE
 	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
+	 * Performs a data type mapping between different databases.
 	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	string	the table name
-	 * @param	string	the column definition
-	 * @param	string	the default value
-	 * @param	bool	should 'NOT NULL' be added
-	 * @param	string	the field after which we should add the new field
-	 * @return	string
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'TINYINT':
+				$attributes['TYPE'] = 'SMALLINT';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'INT':
+				$attributes['TYPE'] = 'INTEGER';
+				return;
+			case 'BIGINT':
+				$attributes['TYPE'] = 'INT64';
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
 	 */
-	protected function _alter_table($alter_type, $table, $column_name, $column_definition = '', $default_value = '', $null = '', $after_field = '')
+	protected function _attr_auto_increment(&$attributes, &$field)
 	{
-		return 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' '.$this->db->escape_identifiers($column_name)
-			.' '.$column_definition
-			.($default_value !== '' ? ' DEFAULT "'.$default_value.'"' : '')
-			.($null === NULL ? ' NULL' : ' NOT NULL')
-			.($after_field !== '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
+		// Not supported
 	}
 
 }
diff --git a/system/database/drivers/mssql/mssql_forge.php b/system/database/drivers/mssql/mssql_forge.php
index 1eef648b0..5eebedbf7 100644
--- a/system/database/drivers/mssql/mssql_forge.php
+++ b/system/database/drivers/mssql/mssql_forge.php
@@ -36,130 +36,98 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 class CI_DB_mssql_forge extends CI_DB_forge {
 
 	/**
-	 * DROP TABLE statement
+	 * CREATE TABLE IF statement
 	 *
 	 * @var	string
 	 */
-	protected $_drop_table	= 'DROP TABLE %s';
-
-	// --------------------------------------------------------------------
+	protected $_create_table_if	= "IF NOT EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'%s') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\nCREATE TABLE";
 
 	/**
-	 * Create Table
+	 * DROP TABLE IF statement
 	 *
-	 * @param	string	the table name
-	 * @param	array	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	string
+	 * @var	string
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
-	{
-		$sql = ($if_not_exists === TRUE)
-			? "IF NOT EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'".$table."') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\n"
-			: '';
-
-		$sql .= 'CREATE TABLE '.$this->db->escape_identifiers($table).' (';
-
-		$current_field_count = 0;
-		foreach ($fields as $field => $attributes)
-		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
-			{
-				$sql .= "\n\t".$attributes;
-			}
-			else
-			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field).' '.$attributes['TYPE'];
+	protected $_drop_table_if	= "IF EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'%s') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\nDROP TABLE";
 
-				if (stripos($attributes['TYPE'], 'INT') === FALSE && ! empty($attributes['CONSTRAINT']))
-				{
-					$sql .= '('.$attributes['CONSTRAINT'].')';
-				}
-
-				if ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
-
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
-
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
-			}
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'TINYINT'	=> 'SMALLINT',
+		'SMALLINT'	=> 'INT',
+		'INT'		=> 'BIGINT',
+		'REAL'		=> 'FLOAT'
+	);
 
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
-			}
-		}
+	// --------------------------------------------------------------------
 
-		if (count($primary_keys) > 0)
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if (in_array($alter_type, array('ADD', 'DROP'), TRUE))
 		{
-			$sql .= ",\n\tPRIMARY KEY (".implode(', ', $this->db->escape_identifiers($primary_keys)).')';
+			return parent::_alter_table($alter_type, $table, $field);
 		}
 
-		if (is_array($keys) && count($keys) > 0)
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' ALTER COLUMN ';
+		$sqls = array();
+		for ($i = 0, $c = count($field); $i < $c; $i++)
 		{
-			foreach ($keys as $key)
-			{
-				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
-					: array($this->db->escape_identifiers($key));
-
-				$sql .= ",\n\tFOREIGN KEY (".implode(', ', $key).')';
-			}
+			$sqls[] = $sql.$this->_process_column($field[$i]);
 		}
 
-		return $sql."\n)";
+		return $sqls;
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
+	 * Field attribute TYPE
 	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
+	 * Performs a data type mapping between different databases.
 	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	string	the table name
-	 * @param	string	the column definition
-	 * @param	string	the default value
-	 * @param	bool	should 'NOT NULL' be added
-	 * @param	string	the field after which we should add the new field
-	 * @return	string
+	 * @param	array	&$attributes
+	 * @return	void
 	 */
-	protected function _alter_table($alter_type, $table, $column_name, $column_definition = '', $default_value = '', $null = '', $after_field = '')
+	protected function _attr_type(&$attributes)
 	{
-		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' '.$this->db->escape_identifiers($column_name);
-
-		// DROP has everything it needs now.
-		if ($alter_type === 'DROP')
+		switch (strtoupper($attributes['TYPE']))
 		{
-			return $sql;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'INTEGER':
+				$attributes['TYPE'] = 'INT';
+				return;
+			default: return;
 		}
+	}
 
-		return $sql.' '.$column_definition
-			.($default_value != '' ? ' DEFAULT "'.$default_value.'"' : '')
-			.($null === NULL ? ' NULL' : ' NOT NULL')
-			.($after_field != '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE)
+		{
+			$field['auto_increment'] = ' IDENTITY(1,1)';
+		}
 	}
 
 }
diff --git a/system/database/drivers/mysql/mysql_forge.php b/system/database/drivers/mysql/mysql_forge.php
index 7ce4e8b00..ea3207760 100644
--- a/system/database/drivers/mysql/mysql_forge.php
+++ b/system/database/drivers/mysql/mysql_forge.php
@@ -42,165 +42,140 @@ class CI_DB_mysql_forge extends CI_DB_forge {
 	 */
 	protected $_create_database	= 'CREATE DATABASE %s CHARACTER SET %s COLLATE %s';
 
-	// --------------------------------------------------------------------
-
 	/**
-	 * Process Fields
+	 * UNSIGNED support
 	 *
-	 * @param	mixed	$fields
-	 * @return	string
+	 * @var	array
 	 */
-	protected function _process_fields($fields)
-	{
-		$current_field_count = 0;
-		$sql = '';
-
-		foreach ($fields as $field => $attributes)
-		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
-			{
-				$sql .= "\n\t".$attributes;
-			}
-			else
-			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field);
-
-				empty($attributes['NAME']) OR $sql .= ' '.$this->db->escape_identifiers($attributes['NAME']).' ';
-
-				if ( ! empty($attributes['TYPE']))
-				{
-					$sql .=  ' '.$attributes['TYPE'];
-
-					if ( ! empty($attributes['CONSTRAINT']))
-					{
-						switch (strtolower($attributes['TYPE']))
-						{
-							case 'decimal':
-							case 'float':
-							case 'numeric':
-								$sql .= '('.implode(',', $attributes['CONSTRAINT']).')';
-								break;
-							case 'enum':
-							case 'set':
-								$sql .= '("'.implode('","', $attributes['CONSTRAINT']).'")';
-								break;
-							default:
-								$sql .= '('.$attributes['CONSTRAINT'].')';
-						}
-					}
-				}
+	protected $_unsigned		= array(
+		'TINYINT',
+		'SMALLINT',
+		'MEDIUMINT',
+		'INT',
+		'INTEGER',
+		'BIGINT',
+		'REAL',
+		'DOUBLE',
+		'DOUBLE PRECISION',
+		'FLOAT',
+		'DECIMAL',
+		'NUMERIC'
+	);
 
-				if ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
-
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= 'NULL';
 
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
-			}
+	// --------------------------------------------------------------------
 
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
-			}
-		}
+	/**
+	 * Class constructor
+	 *
+	 * @return	void
+	 */
+	public function __construct()
+	{
+		parent::__construct();
 
-		return $sql;
+		$this->_create_table .= ' DEFAULT CHARSET '.$this->db->char_set.' COLLATE '.$this->db->dbcollat;
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Create Table
+	 * ALTER TABLE
 	 *
-	 * @param	string	the table name
-	 * @param	mixed	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	bool
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
+	protected function _alter_table($alter_type, $table, $field)
 	{
-		$sql = 'CREATE TABLE ';
-
-		if ($if_not_exists === TRUE)
-		{
-			$sql .= 'IF NOT EXISTS ';
-		}
-
-		$sql .= $this->db->escape_identifiers($table).' ('.$this->_process_fields($fields);
-
-		if (count($primary_keys) > 0)
+		if ($alter_type === 'DROP')
 		{
-			$key_name = $this->db->escape_identifiers(implode('_', $primary_keys));
-			$sql .= ",\n\tPRIMARY KEY ".$key_name.' ('.implode(', ', $this->db->escape_identifiers($primary_keys)).')';
+			return parent::_alter_table($alter_type, $table, $field);
 		}
 
-		if (is_array($keys) && count($keys) > 0)
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		for ($i = 0, $c = count($field); $i < $c; $i++)
 		{
-			foreach ($keys as $key)
+			if ($field[$i]['_literal'] !== FALSE)
 			{
-				if (is_array($key))
+				$field[$i] = ($alter_type === 'ADD')
+						? "\n\tADD ".$field[$i]['_literal']
+						: "\n\tMODIFY ".$field[$i]['_literal'];
+			}
+			else
+			{
+				if ($alter_type === 'ADD')
 				{
-					$key_name = $this->db->escape_identifiers(implode('_', $key));
-					$key = $this->db->escape_identifiers($key);
+					$field[$i]['_literal'] = "\n\tADD ";
 				}
 				else
 				{
-					$key_name = $this->db->escape_identifiers($key);
-					$key = array($key_name);
+					$field[$i]['_literal'] = empty($field['new_name']) ? "\n\tMODIFY " : "\n\tCHANGE ";
 				}
 
-				$sql .= ",\n\tKEY ".$key_name.' ('.implode(', ', $key).')';
+				$field[$i] = $field['_literal'].$this->_process_column($field[$i]);
 			}
 		}
 
-		return $sql."\n) DEFAULT CHARACTER SET ".$this->db->char_set.' COLLATE '.$this->db->dbcollat.';';
+		return array($sql.implode(',', $field));
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
+	 * Process column
 	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column() and column_alter()
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.(empty($field['new_name']) ? '' : $this->db->escape_identifiers($field['new_name']))
+			.' '.$field['type'].$field['length']
+			.$field['unsigned']
+			.$field['null']
+			.$field['default']
+			.$field['auto_increment']
+			.$field['unique'];
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process indexes
 	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	array	fields
-	 * @param	string	the field after which we should add the new field
+	 * @param	string	$table	(ignored)
 	 * @return	string
 	 */
-	protected function _alter_table($alter_type, $table, $fields, $after_field = '')
+	protected function _process_indexes($table = NULL)
 	{
-		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' ';
+		$sql = '';
 
-		// DROP has everything it needs now.
-		if ($alter_type === 'DROP')
+		for ($i = 0, $c = count($this->keys); $i < $c; $i++)
 		{
-			return $sql.$this->db->escape_identifiers($fields);
+			if ( ! isset($this->fields[$this->keys[$i]]))
+			{
+				unset($this->keys[$i]);
+				continue;
+			}
+
+			is_array($this->keys[$i]) OR $this->keys[$i] = array($this->keys[$i]);
+
+			$sql .= ",\n\tKEY ".$this->db->escape_identifiers(implode('_', $this->keys[$i]))
+				.' ('.implode(', ', $this->db->escape_identifiers($this->keys[$i])).')';
 		}
 
-		return $sql.$this->_process_fields($fields)
-			.($after_field !== '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
+		$this->keys = array();
+
+		return $sql;
 	}
 
 }
diff --git a/system/database/drivers/mysqli/mysqli_forge.php b/system/database/drivers/mysqli/mysqli_forge.php
index 0732dfea5..914d6a268 100644
--- a/system/database/drivers/mysqli/mysqli_forge.php
+++ b/system/database/drivers/mysqli/mysqli_forge.php
@@ -42,165 +42,140 @@ class CI_DB_mysqli_forge extends CI_DB_forge {
 	 */
 	protected $_create_database	= 'CREATE DATABASE %s CHARACTER SET %s COLLATE %s';
 
-	// --------------------------------------------------------------------
-
 	/**
-	 * Process Fields
+	 * UNSIGNED support
 	 *
-	 * @param	mixed	$fields
-	 * @return	string
+	 * @var	array
 	 */
-	protected function _process_fields($fields)
-	{
-		$current_field_count = 0;
-		$sql = '';
-
-		foreach ($fields as $field => $attributes)
-		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
-			{
-				$sql .= "\n\t".$attributes;
-			}
-			else
-			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field);
-
-				empty($attributes['NAME']) OR $sql .= ' '.$this->db->escape_identifiers($attributes['NAME']).' ';
-
-				if ( ! empty($attributes['TYPE']))
-				{
-					$sql .= ' '.$attributes['TYPE'];
-
-					if ( ! empty($attributes['CONSTRAINT']))
-					{
-						switch (strtolower($attributes['TYPE']))
-						{
-							case 'decimal':
-							case 'float':
-							case 'numeric':
-								$sql .= '('.implode(',', $attributes['CONSTRAINT']).')';
-								break;
-							case 'enum':
-							case 'set':
-								$sql .= '("'.implode('","', $attributes['CONSTRAINT']).'")';
-								break;
-							default:
-								$sql .= '('.$attributes['CONSTRAINT'].')';
-						}
-					}
-				}
+	protected $_unsigned		= array(
+		'TINYINT',
+		'SMALLINT',
+		'MEDIUMINT',
+		'INT',
+		'INTEGER',
+		'BIGINT',
+		'REAL',
+		'DOUBLE',
+		'DOUBLE PRECISION',
+		'FLOAT',
+		'DECIMAL',
+		'NUMERIC'
+	);
 
-				if ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
-
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= 'NULL';
 
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
-			}
+	// --------------------------------------------------------------------
 
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
-			}
-		}
+	/**
+	 * Class constructor
+	 *
+	 * @return	void
+	 */
+	public function __construct()
+	{
+		parent::__construct();
 
-		return $sql;
+		$this->_create_table .= ' DEFAULT CHARSET '.$this->db->char_set.' COLLATE '.$this->db->dbcollat;
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Create Table
+	 * ALTER TABLE
 	 *
-	 * @param	string	the table name
-	 * @param	mixed	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	bool
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
+	protected function _alter_table($alter_type, $table, $field)
 	{
-		$sql = 'CREATE TABLE ';
-
-		if ($if_not_exists === TRUE)
-		{
-			$sql .= 'IF NOT EXISTS ';
-		}
-
-		$sql .= $this->db->escape_identifiers($table).' ('.$this->_process_fields($fields);
-
-		if (count($primary_keys) > 0)
+		if ($alter_type === 'DROP')
 		{
-			$key_name = $this->db->escape_identifiers(implode('_', $primary_keys));
-			$sql .= ",\n\tPRIMARY KEY ".$key_name.' ('.implode(', ', $this->db->escape_identifiers($primary_keys)).')';
+			return parent::_alter_table($alter_type, $table, $field);
 		}
 
-		if (is_array($keys) && count($keys) > 0)
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		for ($i = 0, $c = count($field); $i < $c; $i++)
 		{
-			foreach ($keys as $key)
+			if ($field[$i]['_literal'] !== FALSE)
 			{
-				if (is_array($key))
+				$field[$i] = ($alter_type === 'ADD')
+						? "\n\tADD ".$field[$i]['_literal']
+						: "\n\tMODIFY ".$field[$i]['_literal'];
+			}
+			else
+			{
+				if ($alter_type === 'ADD')
 				{
-					$key_name = $this->db->escape_identifiers(implode('_', $key));
-					$key = $this->db->escape_identifiers($key);
+					$field[$i]['_literal'] = "\n\tADD ";
 				}
 				else
 				{
-					$key_name = $this->db->escape_identifiers($key);
-					$key = array($key_name);
+					$field[$i]['_literal'] = empty($field['new_name']) ? "\n\tMODIFY " : "\n\tCHANGE ";
 				}
 
-				$sql .= ",\n\tKEY ".$key_name.' ('.implode(', ', $key).')';
+				$field[$i] = $field['_literal'].$this->_process_column($field[$i]);
 			}
 		}
 
-		return $sql."\n) DEFAULT CHARACTER SET ".$this->db->char_set.' COLLATE '.$this->db->dbcollat.';';
+		return array($sql.implode(',', $field));
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
+	 * Process column
 	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.(empty($field['new_name']) ? '' : $this->db->escape_identifiers($field['new_name']))
+			.' '.$field['type'].$field['length']
+			.$field['unsigned']
+			.$field['null']
+			.$field['default']
+			.$field['auto_increment']
+			.$field['unique'];
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process indexes
 	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	array	fields
-	 * @param	string	the field after which we should add the new field
+	 * @param	string	$table	(ignored)
 	 * @return	string
 	 */
-	protected function _alter_table($alter_type, $table, $fields, $after_field = '')
+	protected function _process_indexes($table = NULL)
 	{
-		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' ';
+		$sql = '';
 
-		// DROP has everything it needs now.
-		if ($alter_type === 'DROP')
+		for ($i = 0, $c = count($this->keys); $i < $c; $i++)
 		{
-			return $sql.$this->db->escape_identifiers($fields);
+			if ( ! isset($this->fields[$this->keys[$i]]))
+			{
+				unset($this->keys[$i]);
+				continue;
+			}
+
+			is_array($this->keys[$i]) OR $this->keys[$i] = array($this->keys[$i]);
+
+			$sql .= ",\n\tKEY ".$this->db->escape_identifiers(implode('_', $this->keys[$i]))
+				.' ('.implode(', ', $this->db->escape_identifiers($this->keys[$i])).')';
 		}
 
-		return $sql.$this->_process_fields($fields)
-			.($after_field !== '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
+		$this->keys = array();
+
+		return $sql;
 	}
 
 }
diff --git a/system/database/drivers/oci8/oci8_forge.php b/system/database/drivers/oci8/oci8_forge.php
index ad578f830..bd9d2df3c 100644
--- a/system/database/drivers/oci8/oci8_forge.php
+++ b/system/database/drivers/oci8/oci8_forge.php
@@ -50,126 +50,81 @@ class CI_DB_oci8_forge extends CI_DB_forge {
 	protected $_drop_database	= FALSE;
 
 	/**
-	 * DROP TABLE statement
+	 * DROP TABLE IF statement
 	 *
 	 * @var	string
 	 */
-	protected $_drop_table		= 'DROP TABLE %s';
+	protected $_drop_table_if	= FALSE;
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	bool|array
+	 */
+	protected $_unsigned		= FALSE;
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Create Table
+	 * ALTER TABLE
 	 *
-	 * @param	string	the table name
-	 * @param	array	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	string
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
+	protected function _alter_table($alter_type, $table, $field)
 	{
-		$sql = 'CREATE TABLE ';
-
-		if ($if_not_exists === TRUE)
+		if ($alter_type === 'DROP')
 		{
-			$sql .= 'IF NOT EXISTS ';
+			return parent::_alter_table($alter_type, $table, $field);
+		}
+		elseif ($alter_type === 'CHANGE')
+		{
+			$alter_type = 'MODIFY';
 		}
 
-		$sql .= $this->db->escape_identifiers($table).' (';
-		$current_field_count = 0;
-
-		foreach ($fields as $field => $attributes)
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		$sqls = array();
+		for ($i = 0, $c = count($field); $i < $c; $i++)
 		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
+			if ($field[$i]['_literal'] !== FALSE)
 			{
-				$sql .= "\n\t".$attributes;
+				$field[$i] = "\n\t".$field[$i]['_literal'];
 			}
 			else
 			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field).' '.$attributes['TYPE'];
-
-				if (isset($attributes['UNSINGED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-
-				if (isset($attributes['DEFAULT']))
+				$field[$i]['_literal'] = "\n\t".$this->_process_column($field[$i]);
+				if ($alter_type === 'MODIFY' && ! empty($field[$i]['new_name']))
 				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
+					$sqls[] = $sql.' RENAME COLUMN '.$this->db->escape_identifiers($field[$i]['name'])
+						.' '.$this->db->escape_identifiers($field[$i]['new_name']);
 				}
-
-				$sql .= (isset($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? '' : ' NOT NULL';
-
-				empty($attributes['CONSTRAINT']) OR ' CONSTRAINT '.$attributes['CONSTRAINT'];
-			}
-
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
 			}
 		}
 
-		if (count($primary_keys) > 0)
-		{
-			$sql .= ",\n\tCONSTRAINT ".$table.' PRIMARY KEY ('.implode(', ', $this->db->escape_identifiers($primary_keys)).')';
-		}
+		$sql .= ' '.$alter_type.' ';
+		$sql .= (count($field) === 1)
+				? $fields[0]
+				: '('.implode(',', $field).')';
 
-		if (is_array($keys) && count($keys) > 0)
-		{
-			foreach ($keys as $key)
-			{
-				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
-					: array($this->db->escape_identifiers($key));
-
-				$sql .= ",\n\tUNIQUE COLUMNS (".implode(', ', $key).')';
-			}
-		}
-
-		return $sql."\n)";
+		// RENAME COLUMN must be executed after MODIFY
+		array_unshift($sqls, $sql);
+		return $sql;
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
-	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
+	 * Field attribute AUTO_INCREMENT
 	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	string	the table name
-	 * @param	string	the column definition
-	 * @param	string	the default value
-	 * @param	bool	should 'NOT NULL' be added
-	 * @param	string	the field after which we should add the new field
-	 * @return	string
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
 	 */
-	protected function _alter_table($alter_type, $table, $column_name, $column_definition = '', $default_value = '', $null = '', $after_field = '')
+	protected function _attr_auto_increment(&$attributes, &$field)
 	{
-		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' '.$this->db->escape_identifiers($column_name);
-
-		// DROP has everything it needs now.
-		if ($alter_type === 'DROP')
-		{
-			return $sql;
-		}
-
-		return $sql.' '.$column_definition
-			.($default_value !== '' ? ' DEFAULT "'.$default_value.'"' : '')
-			.($null === NULL ? ' NULL' : ' NOT NULL')
-			.($after_field !== '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
-
+		// Not supported - sequences and triggers must be used instead
 	}
 
 }
diff --git a/system/database/drivers/odbc/odbc_forge.php b/system/database/drivers/odbc/odbc_forge.php
index 699ce996c..fb16ca5cf 100644
--- a/system/database/drivers/odbc/odbc_forge.php
+++ b/system/database/drivers/odbc/odbc_forge.php
@@ -36,130 +36,38 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 class CI_DB_odbc_forge extends CI_DB_forge {
 
 	/**
-	 * DROP TABLE statement
+	 * CREATE TABLE IF statement
 	 *
 	 * @var	string
 	 */
-	protected $_drop_table		= 'DROP TABLE %s';
-
-	// --------------------------------------------------------------------
+	protected $_create_table_if	= FALSE;
 
 	/**
-	 * Create Table
+	 * DROP TABLE IF statement
 	 *
-	 * @param	string	the table name
-	 * @param	array	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	bool
+	 * @var	string
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
-	{
-		$sql = 'CREATE TABLE ';
-
-		if ($if_not_exists === TRUE)
-		{
-			$sql .= 'IF NOT EXISTS ';
-		}
-
-		$sql .= $this->db->escape_identifiers($table).' (';
-		$current_field_count = 0;
-
-		foreach ($fields as $field => $attributes)
-		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
-			{
-				$sql .= "\n\t".$attributes;
-			}
-			else
-			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field).' '.$attributes['TYPE'];
-
-				empty($attributes['CONSTRAINT']) OR $sql .= '('.$attributes['CONSTRAINT'].')';
-
-				if ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
-
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
+	protected $_drop_table_if	= FALSE;
 
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
-			}
-
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
-			}
-		}
-
-		if (count($primary_keys) > 0)
-		{
-			$sql .= ",\n\tPRIMARY KEY (".implode(', ', $this->escape_identifiers($primary_keys)).')';
-		}
-
-		if (is_array($keys) && count($keys) > 0)
-		{
-			foreach ($keys as $key)
-			{
-				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
-					: array($this->db->escape_identifiers($key));
-
-				$sql .= ",\n\tFOREIGN KEY (".implode(', ', $key).')';
-			}
-		}
-
-		return $sql."\n)";
-	}
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	bool|array
+	 */
+	protected $_unsigned		= FALSE;
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
+	 * Field attribute AUTO_INCREMENT
 	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
-	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	string	the table name
-	 * @param	string	the column definition
-	 * @param	string	the default value
-	 * @param	bool	should 'NOT NULL' be added
-	 * @param	string	the field after which we should add the new field
-	 * @return	string
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
 	 */
-	protected function _alter_table($alter_type, $table, $column_name, $column_definition = '', $default_value = '', $null = '', $after_field = '')
+	protected function _attr_auto_increment(&$attributes, &$field)
 	{
-		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' '.$this->db->escape_identifiers($column_name);
-
-		// DROP has everything it needs now.
-		if ($alter_type === 'DROP')
-		{
-			return $sql;
-		}
-
-		return $sql.' '.$column_definition
-			.($default_value != '' ? ' DEFAULT "'.$default_value.'"' : '')
-			.($null === NULL ? ' NULL' : ' NOT NULL')
-			.($after_field != '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
+		// Not supported (in most databases at least)
 	}
 
 }
diff --git a/system/database/drivers/pdo/pdo_forge.php b/system/database/drivers/pdo/pdo_forge.php
index e77970cf2..130d3667e 100644
--- a/system/database/drivers/pdo/pdo_forge.php
+++ b/system/database/drivers/pdo/pdo_forge.php
@@ -36,139 +36,18 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 class CI_DB_pdo_forge extends CI_DB_forge {
 
 	/**
-	 * DROP TABLE statement
+	 * CREATE TABLE IF statement
 	 *
 	 * @var	string
 	 */
-	protected $_drop_table		= 'DROP TABLE %s';
-
-	// --------------------------------------------------------------------
-
-	/**
-	 * Create Table
-	 *
-	 * @param	string	the table name
-	 * @param	array	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	bool
-	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
-	{
-		$sql = 'CREATE TABLE ';
-
-		if ($if_not_exists === TRUE)
-		{
-			$sql .= 'IF NOT EXISTS ';
-		}
-
-		$sql .= $this->db->escape_identifiers($table).' (';
-		$current_field_count = 0;
-
-		foreach ($fields as $field => $attributes)
-		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
-			{
-				$sql .= "\n\t".$attributes;
-			}
-			else
-			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-				$numeric = array('SERIAL', 'INTEGER');
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field).' '.$attributes['TYPE'];
-
-				if ( ! empty($attributes['CONSTRAINT']))
-				{
-					// Exception for Postgre numeric which not too happy with constraint within those type
-					if ( ! ($this->db->subdriver === 'pgsql' && in_array($attributes['TYPE'], $numeric)))
-					{
-						$sql .= '('.$attributes['CONSTRAINT'].')';
-					}
-				}
-
-				if ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
-
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
-
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
-			}
-
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
-			}
-		}
-
-		if (count($primary_keys) > 0)
-		{
-			$sql .= ",\n\tPRIMARY KEY (".implode(', ', $this->db->escape_identifiers($primary_keys)).')';
-		}
-
-		if (is_array($keys) && count($keys) > 0)
-		{
-			foreach ($keys as $key)
-			{
-				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
-					: array($this->db->escape_identifiers($key));
-
-				$sql .= ",\n\tFOREIGN KEY (".implode(', ', $key).')';
-			}
-		}
-
-		return $sql."\n)";
-	}
-
-	// --------------------------------------------------------------------
+	protected $_create_table_if	= FALSE;
 
 	/**
-	 * Alter table query
-	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
+	 * DROP TABLE IF statement
 	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	string	the table name
-	 * @param	string	the column definition
-	 * @param	string	the default value
-	 * @param	bool	should 'NOT NULL' be added
-	 * @param	string	the field after which we should add the new field
-	 * @return	string
+	 * @var	string
 	 */
-	protected function _alter_table($alter_type, $table, $column_name, $column_definition = '', $default_value = '', $null = '', $after_field = '')
-	{
-		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' '.$this->db->escape_identifiers($column_name);
-
-		// DROP has everything it needs now.
-		if ($alter_type === 'DROP')
-		{
-			return $sql;
-		}
-
-		return $sql .' '.$column_definition
-			.($default_value !== '' ? " DEFAULT '".$default_value."'" : '')
-			.($null === NULL ? ' NULL' : ' NOT NULL')
-			.($after_field !== '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
-	}
+	protected $_drop_table_if	= FALSE;
 
 }
 
diff --git a/system/database/drivers/pdo/subdrivers/pdo_4d_forge.php b/system/database/drivers/pdo/subdrivers/pdo_4d_forge.php
new file mode 100644
index 000000000..231ad53a4
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_4d_forge.php
@@ -0,0 +1,209 @@
+<?php
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO 4D Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_4d_forge extends CI_DB_4d_forge {
+
+	/**
+	 * CREATE DATABASE statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_database	= 'CREATE SCHEMA %s';
+
+	/**
+	 * DROP DATABASE statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_database	= 'DROP SCHEMA %s';
+
+	/**
+	 * CREATE TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table_if	= 'CREATE TABLE IF NOT EXISTS';
+
+	/**
+	 * RENAME TABLE statement
+	 *
+	 * @var	string
+	 */
+	protected $_rename_table	= FALSE;
+
+	/**
+	 * DROP TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_table_if	= 'DROP TABLE IF EXISTS';
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'INT16'		=> 'INT',
+		'SMALLINT'	=> 'INT',
+		'INT'		=> 'INT64',
+		'INT32'		=> 'INT64'
+	);
+
+	/**
+	 * DEFAULT value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_default		= FALSE;
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if (in_array($alter_type, array('ADD', 'DROP'), TRUE))
+		{
+			return parent::_alter_table($alter_table, $table, $field);
+		}
+
+		// No method of modifying columns is supported
+		return FALSE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process column
+	 *
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.' '.$field['type'].$field['length']
+			.$field['null']
+			.$field['unique']
+			.$field['auto_increment'];
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'TINYINT':
+				$attributes['TYPE'] = 'SMALLINT';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'INTEGER':
+				$attributes['TYPE'] = 'INT';
+				return;
+			case 'BIGINT':
+				$attribites['TYPE'] = 'INT64';
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute UNIQUE
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_unique(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['UNIQUE']) && $attributes['UNIQUE'] === TRUE)
+		{
+			$field['unique'] = ' UNIQUE';
+
+			// UNIQUE must be used with NOT NULL
+			$field['null'] = ' NOT NULL';
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
+		{
+			if (stripos($field['type'], 'int') !== FALSE)
+			{
+				$field['auto_increment'] = ' AUTO_INCREMENT';
+			}
+			elseif (strcasecmp($field['type'], 'UUID') === 0)
+			{
+				$field['auto_increment'] = ' AUTO_GENERATE';
+			}
+		}
+	}
+
+}
+
+/* End of file pdo_4d_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_4d_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_cubrid_forge.php b/system/database/drivers/pdo/subdrivers/pdo_cubrid_forge.php
new file mode 100644
index 000000000..c01a0fb81
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_cubrid_forge.php
@@ -0,0 +1,173 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO CUBRID Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_cubrid_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * CREATE DATABASE statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_database	= FALSE;
+
+	/**
+	 * DROP DATABASE statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_database	= FALSE;
+
+	/**
+	 * DROP TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_table_if	= 'DROP TABLE IF EXISTS';
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'SHORT'		=> 'INTEGER',
+		'SMALLINT'	=> 'INTEGER',
+		'INT'		=> 'BIGINT',
+		'INTEGER'	=> 'BIGINT',
+		'BIGINT'	=> 'NUMERIC',
+		'FLOAT'		=> 'DOUBLE',
+		'REAL'		=> 'DOUBLE'
+	);
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if (in_array($alter_type, array('DROP', 'ADD'), TRUE))
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
+
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		$sqls = array();
+		for ($i = 0, $c = count($field); $i < $c; $i++)
+		{
+			if ($field[$i]['_literal'] !== FALSE)
+			{
+				$sqls[] = $sql.' CHANGE '.$field[$i]['_literal'];
+			}
+			else
+			{
+				$sqls[] = $sql.' CHANGE '.$this->_process_column($field[$i]);
+				if ( ! empty($field[$i]['new_name']))
+				{
+					$sqls[] = $sql.' RENAME COLUMN '.$this->db->escape_identifiers($field[$i]['name'])
+						.' AS '.$this->db->escape_identifiers($field[$i]['name']);
+				}
+			}
+		}
+
+		return $sqls;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'TINYINT':
+				$attributes['TYPE'] = 'SMALLINT';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process indexes
+	 *
+	 * @param	string	$table	(ignored)
+	 * @return	string
+	 */
+	protected function _process_indexes($table = NULL)
+	{
+		$sql = '';
+
+		for ($i = 0, $c = count($this->keys); $i < $c; $i++)
+		{
+			if ( ! isset($this->fields[$this->keys[$i]]))
+			{
+				unset($this->keys[$i]);
+				continue;
+			}
+
+			is_array($this->keys[$i]) OR $this->keys[$i] = array($this->keys[$i]);
+
+			$sql .= ",\n\tKEY ".$this->db->escape_identifiers(implode('_', $this->keys[$i]))
+				.' ('.implode(', ', $this->db->escape_identifiers($this->keys[$i])).')';
+		}
+
+		$this->keys = array();
+
+		return $sql;
+	}
+
+}
+
+/* End of file pdo_cubrid_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_cubrid_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_dblib_forge.php b/system/database/drivers/pdo/subdrivers/pdo_dblib_forge.php
new file mode 100644
index 000000000..fb33127fd
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_dblib_forge.php
@@ -0,0 +1,136 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO DBLIB Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_dblib_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * CREATE TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table_if	= "IF NOT EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'%s') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\nCREATE TABLE";
+
+	/**
+	 * DROP TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_table_if	= "IF EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'%s') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\nDROP TABLE";
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'TINYINT'	=> 'SMALLINT',
+		'SMALLINT'	=> 'INT',
+		'INT'		=> 'BIGINT',
+		'REAL'		=> 'FLOAT'
+	);
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if (in_array($alter_type, array('ADD', 'DROP'), TRUE))
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
+
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' ALTER COLUMN ';
+		$sqls = array();
+		for ($i = 0, $c = count($field); $i < $c; $i++)
+		{
+			$sqls[] = $sql.$this->_process_column($field[$i]);
+		}
+
+		return $sqls;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'INTEGER':
+				$attributes['TYPE'] = 'INT';
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE)
+		{
+			$field['auto_increment'] = ' IDENTITY(1,1)';
+		}
+	}
+
+}
+
+/* End of file pdo_dblib_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_dblib_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_firebird_forge.php b/system/database/drivers/pdo/subdrivers/pdo_firebird_forge.php
new file mode 100644
index 000000000..88c53510a
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_firebird_forge.php
@@ -0,0 +1,228 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO Firebird Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_firebird_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * RENAME TABLE statement
+	 *
+	 * @var	string
+	 */
+	protected $_rename_table	= FALSE;
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'SMALLINT'	=> 'INTEGER',
+		'INTEGER'	=> 'INT64',
+		'FLOAT'		=> 'DOUBLE PRECISION'
+	);
+
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= 'NULL';
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Create database
+	 *
+	 * @param	string	$db_name
+	 * @return	string
+	 */
+	public function create_database($db_name)
+	{
+		// Firebird databases are flat files, so a path is required
+
+		// Hostname is needed for remote access
+		empty($this->db->hostname) OR $db_name = $this->hostname.':'.$db_name;
+
+		return parent::create_database('"'.$db_name.'"');
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Drop database
+	 *
+	 * @param	string	$db_name	(ignored)
+	 * @return	bool
+	 */
+	public function drop_database($db_name = '')
+	{
+		if ( ! ibase_drop_db($this->conn_id))
+		{
+			return ($this->db->db_debug) ? $this->db->display_error('db_unable_to_drop') : FALSE;
+		}
+		elseif ( ! empty($this->db->data_cache['db_names']))
+		{
+			$key = array_search(strtolower($this->db->database), array_map('strtolower', $this->db->data_cache['db_names']), TRUE);
+			if ($key !== FALSE)
+			{
+				unset($this->db->data_cache['db_names'][$key]);
+			}
+		}
+
+		return TRUE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+ 	{
+		if (in_array($alter_type, array('DROP', 'ADD'), TRUE))
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
+
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		$sqls = array();
+		for ($i = 0, $c = count($field), $sql .= $alter_type.' '; $i < $c; $i++)
+		{
+			if ($field[$i]['_literal'] !== FALSE)
+			{
+				return FALSE;
+			}
+
+			if (isset($field[$i]['type']))
+			{
+				$sqls[] = $sql.' TYPE '.$field[$i]['type'].$field[$i]['length'];
+			}
+
+			if ( ! empty($field[$i]['default']))
+			{
+				$sqls[] = $sql.' ALTER '.$this->db->escape_identifiers($field[$i]['name'])
+					.' SET '.$field[$i]['default'];
+			}
+
+			if (isset($field[$i]['null']))
+			{
+				$sqls[] = 'UPDATE "RDB$RELATION_FIELDS" SET "RDB$NULL_FLAG" = '
+					.($field[$i]['null'] === TRUE ? 'NULL' : '1')
+					.' WHERE "RDB$FIELD_NAME" = '.$this->db->escape($field[$i]['name'])
+					.' AND "RDB$RELATION_NAME" = '.$this->db->escape($table);
+			}
+
+			if ( ! empty($field[$i]['new_name']))
+			{
+				$sqls[] = $sql.' ALTER '.$this->db->escape_identifiers($field[$i]['name'])
+					.' TO '.$this->db->escape_identifiers($field[$i]['new_name']);
+			}
+		}
+
+		return $sqls;
+ 	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process column
+	 *
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.' '.$field['type'].$field['length']
+			.$field['null']
+			.$field['unique']
+			.$field['default'];
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'TINYINT':
+				$attributes['TYPE'] = 'SMALLINT';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'INT':
+				$attributes['TYPE'] = 'INTEGER';
+				return;
+			case 'BIGINT':
+				$attributes['TYPE'] = 'INT64';
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		// Not supported
+	}
+
+}
+
+/* End of file pdo_firebird_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_firebird_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_ibm_forge.php b/system/database/drivers/pdo/subdrivers/pdo_ibm_forge.php
new file mode 100644
index 000000000..6a2c9b87e
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_ibm_forge.php
@@ -0,0 +1,146 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO IBM DB2 Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_ibm_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * RENAME TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_rename_table	= 'RENAME TABLE %s TO %s';
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'SMALLINT'	=> 'INTEGER',
+		'INT'		=> 'BIGINT',
+		'INTEGER'	=> 'BIGINT'
+	);
+
+	/**
+	 * DEFAULT value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_default		= FALSE;
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if ($alter_type === 'CHANGE')
+		{
+			$alter_type = 'MODIFY';
+		}
+
+		return parent::_alter_table($alter_type, $table, $field);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'TINYINT':
+				$attributes['TYPE'] = 'SMALLINT';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute UNIQUE
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_unique(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['UNIQUE']) && $attributes['UNIQUE'] === TRUE)
+		{
+			$field['unique'] = ' UNIQUE';
+
+			// UNIQUE must be used with NOT NULL
+			$field['null'] = ' NOT NULL';
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		// Not supported
+	}
+
+}
+
+/* End of file pdo_ibm_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_ibm_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_informix_forge.php b/system/database/drivers/pdo/subdrivers/pdo_informix_forge.php
new file mode 100644
index 000000000..715a7cbba
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_informix_forge.php
@@ -0,0 +1,155 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO Informix Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_informix_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * RENAME TABLE statement
+	 *
+	 * @var	string
+	 */
+	protected $_rename_table	= 'RENAME TABLE %s TO %s';
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'SMALLINT'	=> 'INTEGER',
+		'INT'		=> 'BIGINT',
+		'INTEGER'	=> 'BIGINT',
+		'REAL'		=> 'DOUBLE PRECISION',
+		'SMALLFLOAT'	=> 'DOUBLE PRECISION'
+	);
+
+	/**
+	 * DEFAULT value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_default		= ', ';
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if ($alter_type === 'CHANGE')
+		{
+			$alter_type = 'MODIFY';
+		}
+
+		return parent::_alter_table($alter_type, $table, $field);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'TINYINT':
+				$attributes['TYPE'] = 'SMALLINT';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'BYTE':
+			case 'TEXT':
+			case 'BLOB':
+			case 'CLOB':
+				$attributes['UNIQUE'] = FALSE;
+				if (isset($attributes['DEFAULT']))
+				{
+					unset($attributes['DEFAULT']);
+				}
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute UNIQUE
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_unique(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['UNIQUE']) && $attributes['UNIQUE'] === TRUE)
+		{
+			$field['unique'] = ' UNIQUE CONSTRAINT '.$this->db->escape_identifiers($field['name']);
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		// Not supported
+	}
+
+}
+
+/* End of file pdo_informix_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_informix_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_mysql_forge.php b/system/database/drivers/pdo/subdrivers/pdo_mysql_forge.php
new file mode 100644
index 000000000..dc856ed2c
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_mysql_forge.php
@@ -0,0 +1,198 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO MySQL Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_mysql_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * CREATE DATABASE statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_database	= 'CREATE DATABASE %s CHARACTER SET %s COLLATE %s';
+
+	/**
+	 * CREATE TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table_if	= 'CREATE TABLE IF NOT EXISTS';
+
+	/**
+	 * DROP TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_table_if	= 'DROP TABLE IF EXISTS';
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'TINYINT',
+		'SMALLINT',
+		'MEDIUMINT',
+		'INT',
+		'INTEGER',
+		'BIGINT',
+		'REAL',
+		'DOUBLE',
+		'DOUBLE PRECISION',
+		'FLOAT',
+		'DECIMAL',
+		'NUMERIC'
+	);
+
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= 'NULL';
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Class constructor
+	 *
+	 * @return	void
+	 */
+	public function __construct()
+	{
+		parent::__construct();
+
+		$this->_create_table .= ' DEFAULT CHARSET '.$this->db->char_set.' COLLATE '.$this->db->dbcollat;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if ($alter_type === 'DROP')
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
+
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		for ($i = 0, $c = count($field); $i < $c; $i++)
+		{
+			if ($field[$i]['_literal'] !== FALSE)
+			{
+				$field[$i] = ($alter_type === 'ADD')
+						? "\n\tADD ".$field[$i]['_literal']
+						: "\n\tMODIFY ".$field[$i]['_literal'];
+			}
+			else
+			{
+				if ($alter_type === 'ADD')
+				{
+					$field[$i]['_literal'] = "\n\tADD ";
+				}
+				else
+				{
+					$field[$i]['_literal'] = empty($field['new_name']) ? "\n\tMODIFY " : "\n\tCHANGE ";
+				}
+
+				$field[$i] = $field['_literal'].$this->_process_column($field[$i]);
+			}
+		}
+
+		return array($sql.implode(',', $field));
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process column
+	 *
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.(empty($field['new_name']) ? '' : $this->db->escape_identifiers($field['new_name']))
+			.' '.$field['type'].$field['length']
+			.$field['unsigned']
+			.$field['null']
+			.$field['default']
+			.$field['auto_increment']
+			.$field['unique'];
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process indexes
+	 *
+	 * @param	string	$table	(ignored)
+	 * @return	string
+	 */
+	protected function _process_indexes($table = NULL)
+	{
+		$sql = '';
+
+		for ($i = 0, $c = count($this->keys); $i < $c; $i++)
+		{
+			if ( ! isset($this->fields[$this->keys[$i]]))
+			{
+				unset($this->keys[$i]);
+				continue;
+			}
+
+			is_array($this->keys[$i]) OR $this->keys[$i] = array($this->keys[$i]);
+
+			$sql .= ",\n\tKEY ".$this->db->escape_identifiers(implode('_', $this->keys[$i]))
+				.' ('.implode(', ', $this->db->escape_identifiers($this->keys[$i])).')';
+		}
+
+		$this->keys = array();
+
+		return $sql;
+	}
+
+}
+
+/* End of file pdo_mysql_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_mysql_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_oci_forge.php b/system/database/drivers/pdo/subdrivers/pdo_oci_forge.php
new file mode 100644
index 000000000..dbcb64d31
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_oci_forge.php
@@ -0,0 +1,133 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO Oracle Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_oci_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * CREATE DATABASE statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_database	= FALSE;
+
+	/**
+	 * DROP DATABASE statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_database	= FALSE;
+
+	/**
+	 * CREATE TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table_if	= 'CREATE TABLE IF NOT EXISTS';
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	bool|array
+	 */
+	protected $_unsigned		= FALSE;
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if ($alter_type === 'DROP')
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
+		elseif ($alter_type === 'CHANGE')
+		{
+			$alter_type = 'MODIFY';
+		}
+
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		$sqls = array();
+		for ($i = 0, $c = count($field); $i < $c; $i++)
+		{
+			if ($field[$i]['_literal'] !== FALSE)
+			{
+				$field[$i] = "\n\t".$field[$i]['_literal'];
+			}
+			else
+			{
+				$field[$i]['_literal'] = "\n\t".$this->_process_column($field[$i]);
+				if ($alter_type === 'MODIFY' && ! empty($field[$i]['new_name']))
+				{
+					$sqls[] = $sql.' RENAME COLUMN '.$this->db->escape_identifiers($field[$i]['name'])
+						.' '.$this->db->escape_identifiers($field[$i]['new_name']);
+				}
+			}
+		}
+
+		$sql .= ' '.$alter_type.' ';
+		$sql .= (count($field) === 1)
+				? $fields[0]
+				: '('.implode(',', $field).')';
+
+		// RENAME COLUMN must be executed after MODIFY
+		array_unshift($sqls, $sql);
+		return $sql;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		// Not supported - sequences and triggers must be used instead
+	}
+
+}
+
+/* End of file pdo_oci_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_oci_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_odbc_forge.php b/system/database/drivers/pdo/subdrivers/pdo_odbc_forge.php
new file mode 100644
index 000000000..cd6b19c68
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_odbc_forge.php
@@ -0,0 +1,62 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO ODBC Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/database/
+ */
+class CI_DB_pdo_odbc_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	bool|array
+	 */
+	protected $_unsigned		= FALSE;
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		// Not supported (in most databases at least)
+	}
+
+}
+
+/* End of file pdo_odbc_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_odbc_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_pgsql_forge.php b/system/database/drivers/pdo/subdrivers/pdo_pgsql_forge.php
new file mode 100644
index 000000000..b5235d24b
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_pgsql_forge.php
@@ -0,0 +1,193 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO PostgreSQL Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_pgsql_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * DROP TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_table_if	= 'DROP TABLE IF EXISTS';
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'INT2'		=> 'INTEGER',
+		'SMALLINT'	=> 'INTEGER',
+		'INT'		=> 'BIGINT',
+		'INT4'		=> 'BIGINT',
+		'INTEGER'	=> 'BIGINT',
+		'INT8'		=> 'NUMERIC',
+		'BIGINT'	=> 'NUMERIC',
+		'REAL'		=> 'DOUBLE PRECISION',
+		'FLOAT'		=> 'DOUBLE PRECISION'
+	);
+
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= 'NULL';
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Class constructor
+	 *
+	 * @return	void
+	 */
+	public function __construct()
+	{
+		parent::__construct();
+
+		if (version_compare($this->db->version(), '9.0', '>'))
+		{
+			$this->create_table_if = 'CREATE TABLE IF NOT EXISTS';
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+ 	{
+		if (in_array($alter_type, array('DROP', 'ADD'), TRUE))
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
+
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		$sqls = array();
+		for ($i = 0, $c = count($field), $sql .= $alter_type.' '; $i < $c; $i++)
+		{
+			if ($field[$i]['_literal'] !== FALSE)
+			{
+				return FALSE;
+			}
+
+			if (version_compare($this->db->version(), '8', '>=') && isset($field[$i]['type']))
+			{
+				$sqls[] = $sql.' TYPE '.$field[$i]['type'].$field[$i]['length'];
+			}
+
+			if ( ! empty($field[$i]['default']))
+			{
+				$sqls[] = $sql.' ALTER '.$this->db->escape_identifiers($field[$i]['name'])
+					.' SET '.$field[$i]['default'];
+			}
+
+			if (isset($field[$i]['null']))
+			{
+				$sqls[] = $sql.' ALTER '.$this->db->escape_identifiers($field[$i]['name'])
+					.($field[$i]['null'] === TRUE ? ' DROP NOT NULL' : ' SET NOT NULL');
+			}
+
+			if ( ! empty($field[$i]['new_name']))
+			{
+				$sqls[] = $sql.' RENAME '.$this->db->escape_identifiers($field[$i]['name'])
+					.' TO '.$this->db->escape_identifiers($field[$i]['new_name']);
+			}
+		}
+
+		return $sqls;
+ 	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		// Reset field lenghts for data types that don't support it
+		if (isset($attributes['CONSTRAINT']) && stripos($attributes['TYPE'], 'int') !== FALSE)
+		{
+			$attributes['CONSTRAINT'] = NULL;
+		}
+
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'TINYINT':
+				$attributes['TYPE'] = 'SMALLINT';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
+		{
+			$field['type'] = ($field['type'] === 'NUMERIC')
+						? 'BIGSERIAL'
+						: 'SERIAL';
+		}
+	}
+
+}
+
+/* End of file pdo_pgsql_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_pgsql_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_sqlite_forge.php b/system/database/drivers/pdo/subdrivers/pdo_sqlite_forge.php
new file mode 100644
index 000000000..414826212
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_sqlite_forge.php
@@ -0,0 +1,228 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.1.6 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO SQLite Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_sqlite_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * CREATE TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table_if	= 'CREATE TABLE IF NOT EXISTS';
+
+	/**
+	 * DROP TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_table_if	= 'DROP TABLE IF EXISTS';
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	bool|array
+	 */
+	protected $_unsigned		= FALSE;
+
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= 'NULL';
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Class constructor
+	 *
+	 * @return	void
+	 */
+	public function __construct()
+	{
+		parent::__construct();
+
+		if (version_compare($this->db->version(), '3.3', '<'))
+		{
+			$this->_create_table_if = FALSE;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Create database
+	 *
+	 * @param	string	$db_name	(ignored)
+	 * @return	bool
+	 */
+	public function create_database($db_name = '')
+	{
+		// In SQLite, a database is created when you connect to the database.
+		// We'll return TRUE so that an error isn't generated
+		return TRUE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Drop database
+	 *
+	 * @param	string	$db_name	(ignored)
+	 * @return	bool
+	 */
+	public function drop_database($db_name = '')
+	{
+		// In SQLite, a database is dropped when we delete a file
+		if (@file_exists($this->db->database))
+		{
+			// We need to close the pseudo-connection first
+			$this->db->close();
+			if ( ! @unlink($this->db->database))
+			{
+				return $this->db->db_debug ? $this->db->display_error('db_unable_to_drop') : FALSE;
+			}
+			elseif ( ! empty($this->db->data_cache['db_names']))
+			{
+				$key = array_search(strtolower($this->db->database), array_map('strtolower', $this->db->data_cache['db_names']), TRUE);
+				if ($key !== FALSE)
+				{
+					unset($this->db->data_cache['db_names'][$key]);
+				}
+			}
+
+			return TRUE;
+		}
+
+		return $this->db->db_debug ? $this->db->display_error('db_unable_to_drop') : FALSE;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if ($alter_type === 'DROP' OR $alter_type === 'CHANGE')
+		{
+			// drop_column():
+			//	BEGIN TRANSACTION;
+			//	CREATE TEMPORARY TABLE t1_backup(a,b);
+			//	INSERT INTO t1_backup SELECT a,b FROM t1;
+			//	DROP TABLE t1;
+			//	CREATE TABLE t1(a,b);
+			//	INSERT INTO t1 SELECT a,b FROM t1_backup;
+			//	DROP TABLE t1_backup;
+			//	COMMIT;
+
+			return FALSE;
+		}
+
+		return parent::_alter_table($alter_type, $table, $field);
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Process column
+	 *
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.' '.$field['type']
+			.$field['auto_increment']
+			.$field['null']
+			.$field['unique']
+			.$field['default'];
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'ENUM':
+			case 'SET':
+				$attributes['TYPE'] = 'TEXT';
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE)
+		{
+			$field['type'] = 'INTEGER PRIMARY KEY';
+			$field['default'] = '';
+			$field['null'] = '';
+			$field['unique'] = '';
+			$field['auto_increment'] = ' AUTOINCREMENT';
+
+			$this->primary_keys = array();
+		}
+	}
+
+}
+
+/* End of file pdo_sqlite_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_sqlite_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_forge.php b/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_forge.php
new file mode 100644
index 000000000..c62720d48
--- /dev/null
+++ b/system/database/drivers/pdo/subdrivers/pdo_sqlsrv_forge.php
@@ -0,0 +1,136 @@
+<?php if ( ! defined('BASEPATH')) exit('No direct script access allowed');
+/**
+ * CodeIgniter
+ *
+ * An open source application development framework for PHP 5.2.4 or newer
+ *
+ * NOTICE OF LICENSE
+ *
+ * Licensed under the Open Software License version 3.0
+ *
+ * This source file is subject to the Open Software License (OSL 3.0) that is
+ * bundled with this package in the files license.txt / license.rst.  It is
+ * also available through the world wide web at this URL:
+ * http://opensource.org/licenses/OSL-3.0
+ * If you did not receive a copy of the license and are unable to obtain it
+ * through the world wide web, please send an email to
+ * licensing@ellislab.com so we can send you a copy immediately.
+ *
+ * @package		CodeIgniter
+ * @author		EllisLab Dev Team
+ * @copyright	Copyright (c) 2008 - 2012, EllisLab, Inc. (http://ellislab.com/)
+ * @license		http://opensource.org/licenses/OSL-3.0 Open Software License (OSL 3.0)
+ * @link		http://codeigniter.com
+ * @since		Version 2.1.0
+ * @filesource
+ */
+defined('BASEPATH') OR exit('No direct script access allowed');
+
+/**
+ * PDO SQLSRV Forge Class
+ *
+ * @category	Database
+ * @author		EllisLab Dev Team
+ * @link		http://codeigniter.com/user_guide/database/
+ */
+class CI_DB_pdo_sqlsrv_forge extends CI_DB_pdo_forge {
+
+	/**
+	 * CREATE TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table_if	= "IF NOT EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'%s') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\nCREATE TABLE";
+
+	/**
+	 * DROP TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_drop_table_if	= "IF EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'%s') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\nDROP TABLE";
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'TINYINT'	=> 'SMALLINT',
+		'SMALLINT'	=> 'INT',
+		'INT'		=> 'BIGINT',
+		'REAL'		=> 'FLOAT'
+	);
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if (in_array($alter_type, array('ADD', 'DROP'), TRUE))
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
+
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' ALTER COLUMN ';
+		$sqls = array();
+		for ($i = 0, $c = count($field); $i < $c; $i++)
+		{
+			$sqls[] = $sql.$this->_process_column($field[$i]);
+		}
+
+		return $sqls;
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
+		{
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'INTEGER':
+				$attributes['TYPE'] = 'INT';
+				return;
+			default: return;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE)
+		{
+			$field['auto_increment'] = ' IDENTITY(1,1)';
+		}
+	}
+
+}
+
+/* End of file pdo_sqlsrv_forge.php */
+/* Location: ./system/database/drivers/pdo/subdrivers/pdo_sqlsrv_forge.php */
\ No newline at end of file
diff --git a/system/database/drivers/postgre/postgre_forge.php b/system/database/drivers/postgre/postgre_forge.php
index b08fa5177..ad26763a4 100644
--- a/system/database/drivers/postgre/postgre_forge.php
+++ b/system/database/drivers/postgre/postgre_forge.php
@@ -36,188 +36,149 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 class CI_DB_postgre_forge extends CI_DB_forge {
 
 	/**
-	 * DROP TABLE statement
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'INT2'		=> 'INTEGER',
+		'SMALLINT'	=> 'INTEGER',
+		'INT'		=> 'BIGINT',
+		'INT4'		=> 'BIGINT',
+		'INTEGER'	=> 'BIGINT',
+		'INT8'		=> 'NUMERIC',
+		'BIGINT'	=> 'NUMERIC',
+		'REAL'		=> 'DOUBLE PRECISION',
+		'FLOAT'		=> 'DOUBLE PRECISION'
+	);
+
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
 	 *
 	 * @var	string
 	 */
-	protected $_drop_table	= 'DROP TABLE IF EXISTS %s CASCADE';
+	protected $_null		= 'NULL';
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Process Fields
+	 * Class constructor
 	 *
-	 * @param	mixed	$fields
-	 * @param	array	$primary_keys
-	 * @return	string
+	 * @return	void
 	 */
-	protected function _process_fields($fields, $primary_keys = array())
+	public function __construct()
 	{
-		$sql = '';
-		$current_field_count = 0;
+		parent::__construct();
 
-		foreach ($fields as $field => $attributes)
+		if (version_compare($this->db->version(), '9.0', '>'))
 		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
+			$this->create_table_if = 'CREATE TABLE IF NOT EXISTS';
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+ 	{
+		if (in_array($alter_type, array('DROP', 'ADD'), TRUE))
+		{
+			return parent::_alter_table($alter_type, $table, $field);
+		}
+
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table);
+		$sqls = array();
+		for ($i = 0, $c = count($field), $sql .= $alter_type.' '; $i < $c; $i++)
+		{
+			if ($field[$i]['_literal'] !== FALSE)
 			{
-				$sql .= "\n\t".$attributes;
+				return FALSE;
 			}
-			else
+
+			if (version_compare($this->db->version(), '8', '>=') && isset($field[$i]['type']))
 			{
-				$sql .= "\n\t".$this->db->escape_identifiers($field);
-
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-				$is_unsigned = ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE);
-
-				// Convert datatypes to be PostgreSQL-compatible
-				switch (strtoupper($attributes['TYPE']))
-				{
-					case 'TINYINT':
-						$attributes['TYPE'] = 'SMALLINT';
-						break;
-					case 'SMALLINT':
-						$attributes['TYPE'] = ($is_unsigned) ? 'INTEGER' : 'SMALLINT';
-						break;
-					case 'MEDIUMINT':
-						$attributes['TYPE'] = 'INTEGER';
-						break;
-					case 'INT':
-						$attributes['TYPE'] = ($is_unsigned) ? 'BIGINT' : 'INTEGER';
-						break;
-					case 'BIGINT':
-						$attributes['TYPE'] = ($is_unsigned) ? 'NUMERIC' : 'BIGINT';
-						break;
-					case 'DOUBLE':
-						$attributes['TYPE'] = 'DOUBLE PRECISION';
-						break;
-					case 'DATETIME':
-						$attributes['TYPE'] = 'TIMESTAMP';
-						break;
-					case 'LONGTEXT':
-						$attributes['TYPE'] = 'TEXT';
-						break;
-					case 'BLOB':
-						$attributes['TYPE'] = 'BYTEA';
-						break;
-					default:
-						break;
-				}
-
-				// If this is an auto-incrementing primary key, use the serial data type instead
-				$sql .= (in_array($field, $primary_keys) && ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-					? ' SERIAL' : ' '.$attributes['TYPE'];
-
-				// Modified to prevent constraints with integer data types
-				if ( ! empty($attributes['CONSTRAINT']) && strpos($attributes['TYPE'], 'INT') === FALSE)
-				{
-					$sql .= '('.$attributes['CONSTRAINT'].')';
-				}
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
-
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
-
-				// Added new attribute to create unique fields. Also works with MySQL
-				if ( ! empty($attributes['UNIQUE']) && $attributes['UNIQUE'] === TRUE)
-				{
-					$sql .= ' UNIQUE';
-				}
+				$sqls[] = $sql.' TYPE '.$field[$i]['type'].$field[$i]['length'];
 			}
 
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
+			if ( ! empty($field[$i]['default']))
 			{
-				$sql .= ',';
+				$sqls[] = $sql.' ALTER '.$this->db->escape_identifiers($field[$i]['name'])
+					.' SET '.$field[$i]['default'];
+			}
+
+			if (isset($field[$i]['null']))
+			{
+				$sqls[] = $sql.' ALTER '.$this->db->escape_identifiers($field[$i]['name'])
+					.($field[$i]['null'] === TRUE ? ' DROP NOT NULL' : ' SET NOT NULL');
+			}
+
+			if ( ! empty($field[$i]['new_name']))
+			{
+				$sqls[] = $sql.' RENAME '.$this->db->escape_identifiers($field[$i]['name'])
+					.' TO '.$this->db->escape_identifiers($field[$i]['new_name']);
 			}
 		}
 
-		return $sql;
-	}
+		return $sqls;
+ 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Create Table
+	 * Field attribute TYPE
 	 *
-	 * @param	string	the table name
-	 * @param	array	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	bool
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
+	protected function _attr_type(&$attributes)
 	{
-		$sql = 'CREATE TABLE ';
-
-		// PostgreSQL doesn't support IF NOT EXISTS syntax so we check if table exists manually
-		if ($if_not_exists === TRUE && $this->db->table_exists($table))
+		// Reset field lenghts for data types that don't support it
+		if (isset($attributes['CONSTRAINT']) && stripos($attributes['TYPE'], 'int') !== FALSE)
 		{
-			return TRUE;
+			$attributes['CONSTRAINT'] = NULL;
 		}
 
-		$sql .= $this->db->escape_identifiers($table).' ('.$this->_process_fields($fields, $primary_keys);
-
-		if (count($primary_keys) > 0)
+		switch (strtoupper($attributes['TYPE']))
 		{
-			$sql .= ",\n\tPRIMARY KEY (".implode(', ', $this->db->escape_identifiers($primary_keys)).')';
-		}
-
-		$sql .= "\n);";
-
-		if (is_array($keys) && count($keys) > 0)
-		{
-			foreach ($keys as $key)
-			{
-				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
-					: array($this->db->escape_identifiers($key));
-
-				foreach ($key as $field)
-				{
-					$sql .= "\nCREATE INDEX ".$this->db->escape_identifiers($table.'_'.str_replace(array('"', "'"), '', $field).'_index')
-						.' ON '.$this->db->escape_identifiers($table).' ('.$this->db->escape_identifiers($field).');';
-				}
-			}
+			case 'TINYINT':
+				$attributes['TYPE'] = 'SMALLINT';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			default: return;
 		}
-
-		return $sql;
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
-	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
+	 * Field attribute AUTO_INCREMENT
 	 *
-	 * @param	string	$alter_type	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	$table		the table name
-	 * @param	string	$fields		the column definition
-	 * @param	string	$after_field
-	 * @return	string
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
 	 */
-	protected function _alter_table($alter_type, $table, $fields, $after_field = '')
- 	{
- 		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' ';
-
- 		// DROP has everything it needs now.
- 		if ($alter_type === 'DROP')
- 		{
- 			return $sql.$this->db->escape_identifiers($fields);
- 		}
-
- 		return $sql.$this->_process_fields($fields)
-			.($after_field !== '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
- 	}
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
+		{
+			$field['type'] = ($field['type'] === 'NUMERIC')
+						? 'BIGSERIAL'
+						: 'SERIAL';
+		}
+	}
 
 }
 
diff --git a/system/database/drivers/sqlite/sqlite_forge.php b/system/database/drivers/sqlite/sqlite_forge.php
index 5650af7be..6ad583560 100644
--- a/system/database/drivers/sqlite/sqlite_forge.php
+++ b/system/database/drivers/sqlite/sqlite_forge.php
@@ -36,9 +36,32 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 class CI_DB_sqlite_forge extends CI_DB_forge {
 
 	/**
+	 * CREATE TABLE IF statement
+	 *
+	 * @var	string
+	 */
+	protected $_create_table_if	= FALSE;
+
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	bool|array
+	 */
+	protected $_unsigned		= FALSE;
+
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= 'NULL';
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Create database
 	 *
-	 * @param	string	the database name
+	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
 	public function create_database($db_name = '')
@@ -53,7 +76,7 @@ class CI_DB_sqlite_forge extends CI_DB_forge {
 	/**
 	 * Drop database
 	 *
-	 * @param	string	the database name (ignored)
+	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
 	public function drop_database($db_name = '')
@@ -77,126 +100,95 @@ class CI_DB_sqlite_forge extends CI_DB_forge {
 	// --------------------------------------------------------------------
 
 	/**
-	 * Create Table
+	 * ALTER TABLE
 	 *
-	 * @param	string	the table name
-	 * @param	array	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	bool
+	 * @todo	implement drop_column(), modify_column()
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
+	protected function _alter_table($alter_type, $table, $field)
 	{
-		$sql = 'CREATE TABLE ';
-
-		// IF NOT EXISTS added to SQLite in 3.3.0
-		if ($if_not_exists === TRUE && version_compare($this->db->version(), '3.3.0', '>=') === TRUE)
+		if ($alter_type === 'DROP' OR $alter_type === 'CHANGE')
 		{
-			$sql .= 'IF NOT EXISTS ';
-		}
-
-		$sql .= $this->db->escape_identifiers($table).' (';
-		$current_field_count = 0;
-
-		foreach ($fields as $field => $attributes)
-		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
-			{
-				$sql .= "\n\t".$attributes;
-			}
-			else
-			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field).' '.$attributes['TYPE'];
-
-				empty($attributes['CONSTRAINT']) OR $sql .= '('.$attributes['CONSTRAINT'].')';
-
-				if ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
+			// drop_column():
+			//	BEGIN TRANSACTION;
+			//	CREATE TEMPORARY TABLE t1_backup(a,b);
+			//	INSERT INTO t1_backup SELECT a,b FROM t1;
+			//	DROP TABLE t1;
+			//	CREATE TABLE t1(a,b);
+			//	INSERT INTO t1 SELECT a,b FROM t1_backup;
+			//	DROP TABLE t1_backup;
+			//	COMMIT;
 
+			return FALSE;
+		}
 
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
+		return parent::_alter_table($alter_type, $table, $field);
+	}
 
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
-			}
+	// --------------------------------------------------------------------
 
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
-			}
-		}
+	/**
+	 * Process column
+	 *
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.' '.$field['type']
+			.$field['auto_increment']
+			.$field['null']
+			.$field['unique']
+			.$field['default'];
+	}
 
-		if (count($primary_keys) > 0)
-		{
-			$sql .= ",\n\tPRIMARY KEY (".implode(', ', $this->db->escape_identifiers($primary_keys)).')';
-		}
+	// --------------------------------------------------------------------
 
-		if (is_array($keys) && count($keys) > 0)
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
 		{
-			foreach ($keys as $key)
-			{
-				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
-					: array($this->db->escape_identifiers($key));
-
-				$sql .= ",\n\tUNIQUE (".implode(', ', $key).')';
-			}
+			case 'ENUM':
+			case 'SET':
+				$attributes['TYPE'] = 'TEXT';
+				return;
+			default: return;
 		}
-
-		return $sql."\n)";
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
+	 * Field attribute AUTO_INCREMENT
 	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
-	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	string	the table name
-	 * @param	string	the column definition
-	 * @param	string	the default value
-	 * @param	bool	should 'NOT NULL' be added
-	 * @param	string	the field after which we should add the new field
-	 * @return	string
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
 	 */
-	protected function _alter_table($alter_type, $table, $column_name, $column_definition = '', $default_value = '', $null = '', $after_field = '')
+	protected function _attr_auto_increment(&$attributes, &$field)
 	{
-		/* SQLite only supports adding new columns and it does
-		 * NOT support the AFTER statement. Each new column will
-		 * be added as the last one in the table.
-		 */
-		if ($alter_type !== 'ADD COLUMN')
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE)
 		{
-			// Not supported
-			return FALSE;
-		}
+			$field['type'] = 'INTEGER PRIMARY KEY';
+			$field['default'] = '';
+			$field['null'] = '';
+			$field['unique'] = '';
+			$field['auto_increment'] = ' AUTOINCREMENT';
 
-		return 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' '.$this->db->escape_identifiers($column_name)
-			.' '.$column_definition
-			.($default_value != '' ? " DEFAULT '".$default_value."'" : '')
-			// If NOT NULL is specified, the field must have a DEFAULT value other than NULL
-			.(($null !== NULL && $default_value !== 'NULL') ? ' NOT NULL' : ' NULL');
+			$this->primary_keys = array();
+		}
 	}
 
 }
diff --git a/system/database/drivers/sqlite3/sqlite3_forge.php b/system/database/drivers/sqlite3/sqlite3_forge.php
index e1dd3fa91..7ba0f7bab 100644
--- a/system/database/drivers/sqlite3/sqlite3_forge.php
+++ b/system/database/drivers/sqlite3/sqlite3_forge.php
@@ -36,9 +36,42 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 class CI_DB_sqlite3_forge extends CI_DB_forge {
 
 	/**
+	 * UNSIGNED support
+	 *
+	 * @var	bool|array
+	 */
+	protected $_unsigned		= FALSE;
+
+	/**
+	 * NULL value representation in CREATE/ALTER TABLE statements
+	 *
+	 * @var	string
+	 */
+	protected $_null		= 'NULL';
+
+	// --------------------------------------------------------------------
+
+	/**
+	 * Class constructor
+	 *
+	 * @return	void
+	 */
+	public function __construct()
+	{
+		parent::__construct();
+
+		if (version_compare($this->db->version(), '3.3', '<'))
+		{
+			$this->create_table_if = FALSE;
+		}
+	}
+
+	// --------------------------------------------------------------------
+
+	/**
 	 * Create database
 	 *
-	 * @param	string	the database name
+	 * @param	string	$db_name
 	 * @return	bool
 	 */
 	public function create_database($db_name = '')
@@ -53,7 +86,7 @@ class CI_DB_sqlite3_forge extends CI_DB_forge {
 	/**
 	 * Drop database
 	 *
-	 * @param	string	the database name (ignored)
+	 * @param	string	$db_name	(ignored)
 	 * @return	bool
 	 */
 	public function drop_database($db_name = '')
@@ -85,125 +118,95 @@ class CI_DB_sqlite3_forge extends CI_DB_forge {
 	// --------------------------------------------------------------------
 
 	/**
-	 * Create Table
+	 * ALTER TABLE
 	 *
-	 * @param	string	the table name
-	 * @param	array	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	bool
+	 * @todo	implement drop_column(), modify_column()
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
+	protected function _alter_table($alter_type, $table, $field)
 	{
-		$sql = 'CREATE TABLE ';
-
-		// IF NOT EXISTS added to SQLite in 3.3.0
-		if ($if_not_exists === TRUE && version_compare($this->db->version(), '3.3.0', '>=') === TRUE)
-		{
-			$sql .= 'IF NOT EXISTS ';
-		}
-
-		$sql .= $this->db->escape_identifiers($table).' (';
-		$current_field_count = 0;
-
-		foreach ($fields as $field => $attributes)
+		if ($alter_type === 'DROP' OR $alter_type === 'CHANGE')
 		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
-			{
-				$sql .= "\n\t".$attributes;
-			}
-			else
-			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field).' '.$attributes['TYPE'];
-
-				empty($attributes['CONSTRAINT']) OR $sql .= '('.$attributes['CONSTRAINT'].')';
-
-				if ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
+			// drop_column():
+			//	BEGIN TRANSACTION;
+			//	CREATE TEMPORARY TABLE t1_backup(a,b);
+			//	INSERT INTO t1_backup SELECT a,b FROM t1;
+			//	DROP TABLE t1;
+			//	CREATE TABLE t1(a,b);
+			//	INSERT INTO t1 SELECT a,b FROM t1_backup;
+			//	DROP TABLE t1_backup;
+			//	COMMIT;
 
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
+			return FALSE;
+		}
 
-				$sql .= ( ! empty($attributes['NULL']) && $attributes['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
+		return parent::_alter_table($alter_type, $table, $field);
+	}
 
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
-			}
+	// --------------------------------------------------------------------
 
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
-			}
-		}
+	/**
+	 * Process column
+	 *
+	 * @param	array	$field
+	 * @return	string
+	 */
+	protected function _process_column($field)
+	{
+		return $this->db->escape_identifiers($field['name'])
+			.' '.$field['type']
+			.$field['auto_increment']
+			.$field['null']
+			.$field['unique']
+			.$field['default'];
+	}
 
-		if (count($primary_keys) > 0)
-		{
-			$sql .= ",\n\tPRIMARY KEY (".implode(', ', $this->db->escape_identifiers($primary_keys)).')';
-		}
+	// --------------------------------------------------------------------
 
-		if (is_array($keys) && count($keys) > 0)
+	/**
+	 * Field attribute TYPE
+	 *
+	 * Performs a data type mapping between different databases.
+	 *
+	 * @param	array	&$attributes
+	 * @return	void
+	 */
+	protected function _attr_type(&$attributes)
+	{
+		switch (strtoupper($attributes['TYPE']))
 		{
-			foreach ($keys as $key)
-			{
-				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
-					: array($this->db->escape_identifiers($key));
-
-				$sql .= ",\n\tUNIQUE (".implode(', ', $key).')';
-			}
+			case 'ENUM':
+			case 'SET':
+				$attributes['TYPE'] = 'TEXT';
+				return;
+			default: return;
 		}
-
-		return $sql."\n)";
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
-	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
+	 * Field attribute AUTO_INCREMENT
 	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	string	the table name
-	 * @param	string	the column definition
-	 * @param	string	the default value
-	 * @param	bool	should 'NOT NULL' be added
-	 * @param	string	the field after which we should add the new field
-	 * @return	string
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
 	 */
-	protected function _alter_table($alter_type, $table, $column_name, $column_definition = '', $default_value = '', $null = '', $after_field = '')
+	protected function _attr_auto_increment(&$attributes, &$field)
 	{
-		/* SQLite only supports adding new columns and it does
-		 * NOT support the AFTER statement. Each new column will
-		 * be added as the last one in the table.
-		 */
-		if ($alter_type !== 'ADD COLUMN')
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE)
 		{
-			// Not supported
-			return FALSE;
-		}
+			$field['type'] = 'INTEGER PRIMARY KEY';
+			$field['default'] = '';
+			$field['null'] = '';
+			$field['unique'] = '';
+			$field['auto_increment'] = ' AUTOINCREMENT';
 
-		return 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' '.$this->db->escape_identifiers($column_name)
-			.' '.$column_definition
-			.($default_value !== '' ? ' DEFAULT '.$default_value : '')
-			// If NOT NULL is specified, the field must have a DEFAULT value other than NULL
-			.(($null !== NULL && $default_value !== 'NULL') ? ' NOT NULL' : ' NULL');
+			$this->primary_keys = array();
+		}
 	}
 
 }
diff --git a/system/database/drivers/sqlsrv/sqlsrv_forge.php b/system/database/drivers/sqlsrv/sqlsrv_forge.php
index 8155565c0..da8f68c56 100644
--- a/system/database/drivers/sqlsrv/sqlsrv_forge.php
+++ b/system/database/drivers/sqlsrv/sqlsrv_forge.php
@@ -36,130 +36,98 @@ defined('BASEPATH') OR exit('No direct script access allowed');
 class CI_DB_sqlsrv_forge extends CI_DB_forge {
 
 	/**
-	 * DROP TABLE statement
+	 * CREATE TABLE IF statement
 	 *
 	 * @var	string
 	 */
-	protected $_drop_table	= 'DROP TABLE %s';
-
-	// --------------------------------------------------------------------
+	protected $_create_table_if	= "IF NOT EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'%s') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\nCREATE TABLE";
 
 	/**
-	 * Create Table
+	 * DROP TABLE IF statement
 	 *
-	 * @param	string	the table name
-	 * @param	array	the fields
-	 * @param	mixed	primary key(s)
-	 * @param	mixed	key(s)
-	 * @param	bool	should 'IF NOT EXISTS' be added to the SQL
-	 * @return	string
+	 * @var	string
 	 */
-	protected function _create_table($table, $fields, $primary_keys, $keys, $if_not_exists)
-	{
-		$sql = ($if_not_exists === TRUE)
-			? "IF NOT EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'".$table."') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\n"
-			: '';
-
-		$sql .= 'CREATE TABLE '.$this->db->escape_identifiers($table).' (';
-
-		$current_field_count = 0;
-		foreach ($fields as $field => $attributes)
-		{
-			// Numeric field names aren't allowed in databases, so if the key is
-			// numeric, we know it was assigned by PHP and the developer manually
-			// entered the field information, so we'll simply add it to the list
-			if (is_numeric($field))
-			{
-				$sql .= "\n\t".$attributes;
-			}
-			else
-			{
-				$attributes = array_change_key_case($attributes, CASE_UPPER);
-
-				$sql .= "\n\t".$this->db->escape_identifiers($field).' '.$attributes['TYPE'];
+	protected $_drop_table_if	= "IF EXISTS (SELECT * FROM sysobjects WHERE ID = object_id(N'%s') AND OBJECTPROPERTY(id, N'IsUserTable') = 1)\nDROP TABLE";
 
-				if (stripos($attributes['TYPE'], 'INT') === FALSE && ! empty($attributes['CONSTRAINT']))
-				{
-					$sql .= '('.$attributes['CONSTRAINT'].')';
-				}
-
-				if ( ! empty($attributes['UNSIGNED']) && $attributes['UNSIGNED'] === TRUE)
-				{
-					$sql .= ' UNSIGNED';
-				}
-
-				if (isset($attributes['DEFAULT']))
-				{
-					$sql .= " DEFAULT '".$attributes['DEFAULT']."'";
-				}
-
-				$sql .= ( ! empty($attributes['NULL']) && $attribues['NULL'] === TRUE)
-					? ' NULL' : ' NOT NULL';
-
-				if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE)
-				{
-					$sql .= ' AUTO_INCREMENT';
-				}
-			}
+	/**
+	 * UNSIGNED support
+	 *
+	 * @var	array
+	 */
+	protected $_unsigned		= array(
+		'TINYINT'	=> 'SMALLINT',
+		'SMALLINT'	=> 'INT',
+		'INT'		=> 'BIGINT',
+		'REAL'		=> 'FLOAT'
+	);
 
-			// don't add a comma on the end of the last field
-			if (++$current_field_count < count($fields))
-			{
-				$sql .= ',';
-			}
-		}
+	// --------------------------------------------------------------------
 
-		if (count($primary_keys) > 0)
+	/**
+	 * ALTER TABLE
+	 *
+	 * @param	string	$alter_type	ALTER type
+	 * @param	string	$table		Table name
+	 * @param	mixed	$field		Column definition
+	 * @return	string|string[]
+	 */
+	protected function _alter_table($alter_type, $table, $field)
+	{
+		if (in_array($alter_type, array('ADD', 'DROP'), TRUE))
 		{
-			$sql .= ",\n\tPRIMARY KEY (".implode(', ', $this->db->escape_identifiers($primary_keys)).')';
+			return parent::_alter_table($alter_type, $table, $field);
 		}
 
-		if (is_array($keys) && count($keys) > 0)
+		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' ALTER COLUMN ';
+		$sqls = array();
+		for ($i = 0, $c = count($field); $i < $c; $i++)
 		{
-			foreach ($keys as $key)
-			{
-				$key = is_array($key)
-					? $this->db->escape_identifiers($key)
-					: array($this->escape_identifiers($key));
-
-				$sql .= ",\n\tFOREIGN KEY (".implode(', ', $key).')';
-			}
+			$sqls[] = $sql.$this->_process_column($field[$i]);
 		}
 
-		return $sql."\n)";
+		return $sqls;
 	}
 
 	// --------------------------------------------------------------------
 
 	/**
-	 * Alter table query
+	 * Field attribute TYPE
 	 *
-	 * Generates a platform-specific query so that a table can be altered
-	 * Called by add_column(), drop_column(), and column_alter(),
+	 * Performs a data type mapping between different databases.
 	 *
-	 * @param	string	the ALTER type (ADD, DROP, CHANGE)
-	 * @param	string	the column name
-	 * @param	string	the table name
-	 * @param	string	the column definition
-	 * @param	string	the default value
-	 * @param	bool	should 'NOT NULL' be added
-	 * @param	string	the field after which we should add the new field
-	 * @return	string
+	 * @param	array	&$attributes
+	 * @return	void
 	 */
-	protected function _alter_table($alter_type, $table, $column_name, $column_definition = '', $default_value = '', $null = '', $after_field = '')
+	protected function _attr_type(&$attributes)
 	{
-		$sql = 'ALTER TABLE '.$this->db->escape_identifiers($table).' '.$alter_type.' '.$this->db->escape_identifiers($column_name);
-
-		// DROP has everything it needs now.
-		if ($alter_type === 'DROP')
+		switch (strtoupper($attributes['TYPE']))
 		{
-			return $sql;
+			case 'MEDIUMINT':
+				$attributes['TYPE'] = 'INTEGER';
+				$attributes['UNSIGNED'] = FALSE;
+				return;
+			case 'INTEGER':
+				$attributes['TYPE'] = 'INT';
+				return;
+			default: return;
 		}
+	}
 
-		return $sql.' '.$column_definition
-			.($default_value != '' ? ' DEFAULT "'.$default_value.'"' : '')
-			.($null === NULL ? ' NULL' : ' NOT NULL')
-			.($after_field != '' ? ' AFTER '.$this->db->escape_identifiers($after_field) : '');
+	// --------------------------------------------------------------------
+
+	/**
+	 * Field attribute AUTO_INCREMENT
+	 *
+	 * @param	array	&$attributes
+	 * @param	array	&$field
+	 * @return	void
+	 */
+	protected function _attr_auto_increment(&$attributes, &$field)
+	{
+		if ( ! empty($attributes['AUTO_INCREMENT']) && $attributes['AUTO_INCREMENT'] === TRUE && stripos($field['type'], 'int') !== FALSE)
+		{
+			$field['auto_increment'] = ' IDENTITY(1,1)';
+		}
 	}
 
 }
diff --git a/tests/mocks/database/db/driver.php b/tests/mocks/database/db/driver.php
index 65ac2c4cc..2cf54b97b 100644
--- a/tests/mocks/database/db/driver.php
+++ b/tests/mocks/database/db/driver.php
@@ -34,6 +34,7 @@ class Mock_Database_DB_Driver extends CI_DB_driver {
 
 		return call_user_func_array(array($this->ci_db_driver, $method), $arguments);
 	}
+
 }
 
 class CI_DB extends Mock_Database_DB_QueryBuilder {}
\ No newline at end of file
diff --git a/tests/mocks/database/schema/skeleton.php b/tests/mocks/database/schema/skeleton.php
index d72244528..e5c536090 100644
--- a/tests/mocks/database/schema/skeleton.php
+++ b/tests/mocks/database/schema/skeleton.php
@@ -69,7 +69,7 @@ class Mock_Database_Schema_Skeleton {
 			)
 		));
 		static::$forge->add_key('id', TRUE);
-		static::$forge->create_table('user', (strpos(static::$driver, 'pgsql') === FALSE));
+		static::$forge->create_table('user', TRUE);
 
 		// Job Table
 		static::$forge->add_field(array(
@@ -86,7 +86,7 @@ class Mock_Database_Schema_Skeleton {
 			)
 		));
 		static::$forge->add_key('id', TRUE);
-		static::$forge->create_table('job', (strpos(static::$driver, 'pgsql') === FALSE));
+		static::$forge->create_table('job', TRUE);
 
 		// Misc Table
 		static::$forge->add_field(array(
@@ -103,7 +103,7 @@ class Mock_Database_Schema_Skeleton {
 			)
 		));
 		static::$forge->add_key('id', TRUE);
-		static::$forge->create_table('misc', (strpos(static::$driver, 'pgsql') === FALSE));
+		static::$forge->create_table('misc', TRUE);
 	}
 
 	/**
diff --git a/user_guide_src/source/changelog.rst b/user_guide_src/source/changelog.rst
index cbc6295c8..717d7f6ba 100644
--- a/user_guide_src/source/changelog.rst
+++ b/user_guide_src/source/changelog.rst
@@ -154,6 +154,8 @@ Release Date: Not Released
    -  Added MySQL client compression support.
    -  Added encrypted connections support (for *mysql*, *sqlsrv* and PDO with *sqlsrv*).
    -  Removed :doc:`Loader Class <libraries/loader>` from Database error tracing to better find the likely culprit.
+   -  Added an optional second parameter to ``drop_table()`` in :doc:`Database Forge <database/forge>` that allows adding the IF EXISTS condition.
+   -  Removed the optional AFTER clause from :doc:`Database Forge <database/forge>` method ``add_column()``.
 
 -  Libraries
 
diff --git a/user_guide_src/source/database/forge.rst b/user_guide_src/source/database/forge.rst
index bf17e2918..1d6b847b4 100644
--- a/user_guide_src/source/database/forge.rst
+++ b/user_guide_src/source/database/forge.rst
@@ -193,13 +193,15 @@ into the definition
 Dropping a table
 ================
 
-Executes a DROP TABLE sql
+Execute a DROP TABLE statement and optionally add an IF EXISTS clause.
 
 ::
 
+	// Produces: DROP TABLE table_name
 	$this->dbforge->drop_table('table_name');
-	// gives DROP TABLE IF EXISTS  table_name
 
+	// Produces: DROP TABLE IF EXISTS table_name
+	$this->dbforge->drop_table('table_name');
 
 Renaming a table
 ================
@@ -231,14 +233,6 @@ number of additional fields.
 	$this->dbforge->add_column('table_name', $fields); 
 	// gives ALTER TABLE table_name ADD preferences TEXT
 
-An optional third parameter can be used to specify which existing column
-to add the new column after.
-
-::
-
-	$this->dbforge->add_column('table_name', $fields, 'after_field');
-
-
 $this->dbforge->drop_column()
 ==============================
 
diff --git a/user_guide_src/source/installation/upgrade_300.rst b/user_guide_src/source/installation/upgrade_300.rst
index fd5eea478..4e0b952d5 100644
--- a/user_guide_src/source/installation/upgrade_300.rst
+++ b/user_guide_src/source/installation/upgrade_300.rst
@@ -93,9 +93,31 @@ Step 8: Check the calls to Array Helper's element() and elements() functions
 The default return value of these functions, when the required elements
 don't exist, has been changed from FALSE to NULL.
 
-**********************************************************
-Step 9: Change usage of Email library with multiple emails
-**********************************************************
+************************************************************
+Step 9: Update usage of Database Forge's drop_table() method
+************************************************************
+
+Up until now, ``drop_table()`` added an IF EXISTS clause by default or it didn't work
+at all with some drivers. In CodeIgniter 3.0, the IF EXISTS condition is no longer added
+by deafault and has an optional second parameter that allows that instead and is set to
+FALSE by default.
+
+If your application relies on IF EXISTS, you'll have to change its usage.
+
+::
+
+	// Now produces just DROP TABLE `table_name`
+	$this->dbforge->drop_table('table_name');
+
+	// Produces DROP TABLE IF EXISTS `table_name`
+	$this->dbforge->drop_table('table_name', TRUE);
+
+.. note:: The given example users MySQL-specific syntax, but it should work across
+	all drivers with the exception of ODBC.
+
+***********************************************************
+Step 10: Change usage of Email library with multiple emails
+***********************************************************
 
 The :doc:`Email library <../libraries/email>` will automatically clear the
 set parameters after successfully sending emails. To override this behaviour,
@@ -110,7 +132,7 @@ pass FALSE as the first parameter in the ``send()`` method:
 
 
 ****************************************************************
-Step 10: Remove usage of (previously) deprecated functionalities
+Step 11: Remove usage of (previously) deprecated functionalities
 ****************************************************************
 
 In addition to the ``$autoload['core']`` configuration setting, there's a number of other functionalities