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-#######
-Queries
-#######
-
-************
-Query Basics
-************
-
-Regular Queries
-===============
-
-To submit a query, use the **query** function::
-
- $this->db->query('YOUR QUERY HERE');
-
-The query() function returns a database result **object** when "read"
-type queries are run, which you can use to :doc:`show your
-results <results>`. When "write" type queries are run it simply
-returns TRUE or FALSE depending on success or failure. When retrieving
-data you will typically assign the query to your own variable, like
-this::
-
- $query = $this->db->query('YOUR QUERY HERE');
-
-Simplified Queries
-==================
-
-The **simple_query** method is a simplified version of the
-$this->db->query() method. It DOES
-NOT return a database result set, nor does it set the query timer, or
-compile bind data, or store your query for debugging. It simply lets you
-submit a query. Most users will rarely use this function.
-
-It returns whatever the database drivers' "execute" function returns.
-That typically is TRUE/FALSE on success or failure for write type queries
-such as INSERT, DELETE or UPDATE statements (which is what it really
-should be used for) and a resource/object on success for queries with
-fetchable results.
-
-::
-
- if ($this->db->simple_query('YOUR QUERY'))
- {
- echo "Success!";
- }
- else
- {
- echo "Query failed!";
- }
-
-.. note:: PostgreSQL's ``pg_exec()`` function (for example) always
- returns a resource on success, even for write type queries.
- So take that in mind if you're looking for a boolean value.
-
-***************************************
-Working with Database prefixes manually
-***************************************
-
-If you have configured a database prefix and would like to prepend it to
-a table name for use in a native SQL query for example, then you can use
-the following::
-
- $this->db->dbprefix('tablename'); // outputs prefix_tablename
-
-
-If for any reason you would like to change the prefix programatically
-without needing to create a new connection, you can use this method::
-
- $this->db->set_dbprefix('newprefix');
- $this->db->dbprefix('tablename'); // outputs newprefix_tablename
-
-
-**********************
-Protecting identifiers
-**********************
-
-In many databases it is advisable to protect table and field names - for
-example with backticks in MySQL. **Query Builder queries are
-automatically protected**, however if you need to manually protect an
-identifier you can use::
-
- $this->db->protect_identifiers('table_name');
-
-.. important:: Although the Query Builder will try its best to properly
- quote any field and table names that you feed it, note that it
- is NOT designed to work with arbitrary user input. DO NOT feed it
- with unsanitized user data.
-
-This function will also add a table prefix to your table, assuming you
-have a prefix specified in your database config file. To enable the
-prefixing set TRUE (boolean) via the second parameter::
-
- $this->db->protect_identifiers('table_name', TRUE);
-
-
-****************
-Escaping Queries
-****************
-
-It's a very good security practice to escape your data before submitting
-it into your database. CodeIgniter has three methods that help you do
-this:
-
-#. **$this->db->escape()** This function determines the data type so
- that it can escape only string data. It also automatically adds
- single quotes around the data so you don't have to:
- ::
-
- $sql = "INSERT INTO table (title) VALUES(".$this->db->escape($title).")";
-
-#. **$this->db->escape_str()** This function escapes the data passed to
- it, regardless of type. Most of the time you'll use the above
- function rather than this one. Use the function like this:
- ::
-
- $sql = "INSERT INTO table (title) VALUES('".$this->db->escape_str($title)."')";
-
-#. **$this->db->escape_like_str()** This method should be used when
- strings are to be used in LIKE conditions so that LIKE wildcards
- ('%', '\_') in the string are also properly escaped.
-
-::
-
- $search = '20% raise';
- $sql = "SELECT id FROM table WHERE column LIKE '%" .
- $this->db->escape_like_str($search)."%' ESCAPE '!'";
-
-.. important:: The ``escape_like_str()`` method uses '!' (exclamation mark)
- to escape special characters for *LIKE* conditions. Because this
- method escapes partial strings that you would wrap in quotes
- yourself, it cannot automatically add the ``ESCAPE '!'``
- condition for you, and so you'll have to manually do that.
-
-
-**************
-Query Bindings
-**************
-
-Bindings enable you to simplify your query syntax by letting the system
-put the queries together for you. Consider the following example::
-
- $sql = "SELECT * FROM some_table WHERE id = ? AND status = ? AND author = ?";
- $this->db->query($sql, array(3, 'live', 'Rick'));
-
-The question marks in the query are automatically replaced with the
-values in the array in the second parameter of the query function.
-
-Binding also work with arrays, which will be transformed to IN sets::
-
- $sql = "SELECT * FROM some_table WHERE id IN ? AND status = ? AND author = ?";
- $this->db->query($sql, array(array(3, 6), 'live', 'Rick'));
-
-The resulting query will be::
-
- SELECT * FROM some_table WHERE id IN (3,6) AND status = 'live' AND author = 'Rick'
-
-The secondary benefit of using binds is that the values are
-automatically escaped, producing safer queries. You don't have to
-remember to manually escape data; the engine does it automatically for
-you.
-
-***************
-Handling Errors
-***************
-
-**$this->db->error();**
-
-If you need to get the last error that has occurred, the error() method
-will return an array containing its code and message. Here's a quick
-example::
-
- if ( ! $this->db->simple_query('SELECT `example_field` FROM `example_table`'))
- {
- $error = $this->db->error(); // Has keys 'code' and 'message'
- }
-