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#################
Database Metadata
#################
**************
Table MetaData
**************
These functions let you fetch table information.
List the Tables in Your Database
================================
**$this->db->list_tables();**
Returns an array containing the names of all the tables in the database
you are currently connected to. Example::
$tables = $this->db->list_tables();
foreach ($tables as $table)
{
echo $table;
}
Determine If a Table Exists
===========================
**$this->db->table_exists();**
Sometimes it's helpful to know whether a particular table exists before
running an operation on it. Returns a boolean TRUE/FALSE. Usage example::
if ($this->db->table_exists('table_name'))
{
// some code...
}
.. note:: Replace *table_name* with the name of the table you are looking for.
**************
Field MetaData
**************
List the Fields in a Table
==========================
**$this->db->list_fields()**
Returns an array containing the field names. This query can be called
two ways:
1. You can supply the table name and call it from the $this->db->
object::
$fields = $this->db->list_fields('table_name');
foreach ($fields as $field)
{
echo $field;
}
2. You can gather the field names associated with any query you run by
calling the function from your query result object::
$query = $this->db->query('SELECT * FROM some_table');
foreach ($query->list_fields() as $field)
{
echo $field;
}
Determine If a Field is Present in a Table
==========================================
**$this->db->field_exists()**
Sometimes it's helpful to know whether a particular field exists before
performing an action. Returns a boolean TRUE/FALSE. Usage example::
if ($this->db->field_exists('field_name', 'table_name'))
{
// some code...
}
.. note:: Replace *field_name* with the name of the column you are looking
for, and replace *table_name* with the name of the table you are
looking for.
Retrieve Field Metadata
=======================
**$this->db->field_data()**
Returns an array of objects containing field information.
Sometimes it's helpful to gather the field names or other metadata, like
the column type, max length, etc.
.. note:: Not all databases provide meta-data.
Usage example::
$fields = $this->db->field_data('table_name');
foreach ($fields as $field)
{
echo $field->name;
echo $field->type;
echo $field->max_length;
echo $field->primary_key;
}
If you have run a query already you can use the result object instead of
supplying the table name::
$query = $this->db->query("YOUR QUERY");
$fields = $query->field_data();
The following data is available from this function if supported by your
database:
- name - column name
- max_length - maximum length of the column
- primary_key - 1 if the column is a primary key
- type - the type of the column
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