Database Forge Class

The Database Forge Class contains methods that help you manage your database.

Table of Contents

• Database Forge Class
  • Initializing the Forge Class
  • Creating and Dropping Databases
  • Creating and Dropping Tables
    • Adding fields
    • Adding Keys
    • Creating a table
    • Dropping a table
    • Renaming a table
  • Modifying Tables
    • Adding a Column to a Table
    • Dropping a Column From a Table
    • Modifying a Column in a Table
  • Class Reference

Initializing the Forge Class

Load the Forge Class as follows:

$this->load->dbforge()

You can also pass another database object to the DB Forge loader, in case the database you want to manage isn’t the default one:

$this->myforge = $this->load->dbforge($this->other_db, TRUE);

In the above example, we’re passing a custom database object as the first parameter and then tell it to return the dbforge object, instead of assigning it directly to $this->dbforge.

Once initialized you will access the methods using the $this->dbforge object:

$this->dbforge->some_method();

Creating and Dropping Databases

$this->dbforge->create_database(‘db_name’)

Permits you to create the database specified in the first parameter. Returns TRUE/FALSE based on success or failure:

if ($this->dbforge->create_database('my_db'))
{
        echo 'Database created!';
}

$this->dbforge->drop_database(‘db_name’)

Permits you to drop the database specified in the first parameter. Returns TRUE/FALSE based on success or failure:

if ($this->dbforge->drop_database('my_db'))
{
        echo 'Database deleted!';
}

Creating and Dropping Tables

There are several things you may wish to do when creating tables. Add fields, add keys to the table, alter columns. CodeIgniter provides a mechanism for this.

Adding fields

Fields are created via an associative array. Within the array you must include a ‘type’ key that relates to the datatype of the field. For example, INT, VARCHAR, TEXT, etc. Many datatypes (for example VARCHAR) also require a ‘constraint’ key.

$fields = array(
        'users' => array(
                'type' => 'VARCHAR',
                'constraint' => '100',
        ),
);
// will translate to "users VARCHAR(100)" when the field is added.

Additionally, the following key/values can be used:

• unsigned/true : to generate “UNSIGNED” in the field definition.
• default/value : to generate a default value in the field definition.
• null/true : to generate “NULL” in the field definition. Without this, the field will default to “NOT NULL”.
• auto_increment/true : generates an auto_increment flag on the field. Note that the field type must be a type that supports this, such as integer.
• unique/true : to generate a unique key for the field definition.

$fields = array(
        'blog_id' => array(
                'type' => 'INT',
                'constraint' => 5,
                'unsigned' => TRUE,
                'auto_increment' => TRUE
        ),
        'blog_title' => array(
                'type' => 'VARCHAR',
                'constraint' => '100',
                'unique' => TRUE,
        ),
        'blog_author' => array(
                'type' =>'VARCHAR',
                'constraint' => '100',
                'default' => 'King of Town',
        ),
        'blog_description' => array(
                'type' => 'TEXT',
                'null' => TRUE,
        ),
);

After the fields have been defined, they can be added using $this->dbforge->add_field($fields); followed by a call to the create_table() method.

$this->dbforge->add_field()

The add fields method will accept the above array.

Passing strings as fields

If you know exactly how you want a field to be created, you can pass the string into the field definitions with add_field()

$this->dbforge->add_field("label varchar(100) NOT NULL DEFAULT 'default label'");

Creating an id field

There is a special exception for creating id fields. A field with type id will automatically be assigned as an INT(9) auto_incrementing Primary Key.

$this->dbforge->add_field('id');
// gives id INT(9) NOT NULL AUTO_INCREMENT

Adding Keys

Generally speaking, you’ll want your table to have Keys. This is accomplished with $this->dbforge->add_key(‘field’). An optional second parameter set to TRUE will make it a primary key. Note that add_key() must be followed by a call to create_table().

Multiple column non-primary keys must be sent as an array. Sample output below is for MySQL.

$this->dbforge->add_key('blog_id', TRUE);
// gives PRIMARY KEY `blog_id` (`blog_id`)

$this->dbforge->add_key('blog_id', TRUE);
$this->dbforge->add_key('site_id', TRUE);
// gives PRIMARY KEY `blog_id_site_id` (`blog_id`, `site_id`)

$this->dbforge->add_key('blog_name');
// gives KEY `blog_name` (`blog_name`)

$this->dbforge->add_key(array('blog_name', 'blog_label'));
// gives KEY `blog_name_blog_label` (`blog_name`, `blog_label`)

Creating a table

After fields and keys have been declared, you can create a new table with

$this->dbforge->create_table('table_name');
// gives CREATE TABLE table_name

An optional second parameter set to TRUE adds an “IF NOT EXISTS” clause into the definition

$this->dbforge->create_table('table_name', TRUE);
// gives CREATE TABLE IF NOT EXISTS table_name

You could also pass optional table attributes, such as MySQL’s ENGINE:

$attributes = array('ENGINE' => 'InnoDB');
$this->dbforge->create_table('table_name', FALSE, $attributes);
// produces: CREATE TABLE `table_name` (...) ENGINE = InnoDB DEFAULT CHARACTER SET utf8 COLLATE utf8_general_ci

Dropping a table

Execute a DROP TABLE statement and optionally add an IF EXISTS clause.

// Produces: DROP TABLE table_name
$this->dbforge->drop_table('table_name');

// Produces: DROP TABLE IF EXISTS table_name
$this->dbforge->drop_table('table_name',TRUE);

Renaming a table

Executes a TABLE rename

$this->dbforge->rename_table('old_table_name', 'new_table_name');
// gives ALTER TABLE old_table_name RENAME TO new_table_name

Modifying Tables

Adding a Column to a Table

$this->dbforge->add_column()

The add_column() method is used to modify an existing table. It accepts the same field array as above, and can be used for an unlimited number of additional fields.

$fields = array(
        'preferences' => array('type' => 'TEXT')
);
$this->dbforge->add_column('table_name', $fields);
// Executes: ALTER TABLE table_name ADD preferences TEXT

If you are using MySQL or CUBIRD, then you can take advantage of their AFTER and FIRST clauses to position the new column.

Examples:

// Will place the new column after the `another_field` column:
$fields = array(
        'preferences' => array('type' => 'TEXT', 'after' => 'another_field')
);

// Will place the new column at the start of the table definition:
$fields = array(
        'preferences' => array('type' => 'TEXT', 'first' => TRUE)
);

Dropping a Column From a Table

$this->dbforge->drop_column()

Used to remove a column from a table.

$this->dbforge->drop_column('table_name', 'column_to_drop');

Modifying a Column in a Table

$this->dbforge->modify_column()

The usage of this method is identical to add_column(), except it alters an existing column rather than adding a new one. In order to change the name you can add a “name” key into the field defining array.

$fields = array(
        'old_name' => array(
                'name' => 'new_name',
                'type' => 'TEXT',
        ),
);
$this->dbforge->modify_column('table_name', $fields);
// gives ALTER TABLE table_name CHANGE old_name new_name TEXT

Class Reference

class CI_DB_forge

add_column($table[, $field = array()[, $_after = NULL]])

Parameters:	$table (string) – Table name to add the column to $field (array) – Column definition(s) $_after (string) – Column for AFTER clause (deprecated)
Returns:	TRUE on success, FALSE on failure
Return type:	bool

Adds a column to a table. Usage: See Adding a Column to a Table.

add_field($field)

Parameters:	$field (array) – Field definition to add
Returns:	CI_DB_forge instance (method chaining)
Return type:	CI_DB_forge

Adds a field to the set that will be used to create a table. Usage: See Adding fields.

add_key($key[, $primary = FALSE])

Parameters:	$key (array) – Name of a key field $primary (bool) – Set to TRUE if it should be a primary key or a regular one
Returns:	CI_DB_forge instance (method chaining)
Return type:	CI_DB_forge

Adds a key to the set that will be used to create a table. Usage: See Adding Keys.

create_database($db_name)

Parameters:	$db_name (string) – Name of the database to create
Returns:	TRUE on success, FALSE on failure
Return type:	bool

Creates a new database. Usage: See Creating and Dropping Databases.

create_table($table[, $if_not_exists = FALSE[, array $attributes = array()]])

Parameters:	$table (string) – Name of the table to create $if_not_exists (string) – Set to TRUE to add an ‘IF NOT EXISTS’ clause $attributes (string) – An associative array of table attributes
Returns:	TRUE on success, FALSE on failure
Return type:	bool

Creates a new table. Usage: See Creating a table.

drop_column($table, $column_name)

Parameters:	$table (string) – Table name $column_name (array) – The column name to drop
Returns:	TRUE on success, FALSE on failure
Return type:	bool

Drops a column from a table. Usage: See Dropping a Column From a Table.

drop_database($db_name)

Parameters:	$db_name (string) – Name of the database to drop
Returns:	TRUE on success, FALSE on failure
Return type:	bool

Drops a database. Usage: See Creating and Dropping Databases.

drop_table($table_name[, $if_exists = FALSE])

Parameters:	$table (string) – Name of the table to drop $if_exists (string) – Set to TRUE to add an ‘IF EXISTS’ clause
Returns:	TRUE on success, FALSE on failure
Return type:	bool

Drops a table. Usage: See Dropping a table.

modify_column($table, $field)

Parameters:	$table (string) – Table name $field (array) – Column definition(s)
Returns:	TRUE on success, FALSE on failure
Return type:	bool

Modifies a table column. Usage: See Modifying a Column in a Table.

rename_table($table_name, $new_table_name)

Parameters:	$table (string) – Current of the table $new_table_name (string) – New name of the table
Returns:	TRUE on success, FALSE on failure
Return type:	bool

Renames a table. Usage: See Renaming a table.