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Database Forge Class
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<h1>Database Forge Class</h1>
<p>The Database Forge Class contains functions that help you manage your database.</p>
<h3>Table of Contents</h3>
<ul>
<li><a href="#init">Initializing the Forge Class</a></li>
<li><a href="#create">Creating a Database</a></li>
<li><a href="#drop">Dropping a Database</a></li>
<li><a href="#add_field">Adding Fields</a></li>
<li><a href="#add_key">Adding Keys</a></li>
<li><a href="#create_table">Creating a Table</a></li>
<li><a href="#drop_table">Dropping a Table</a></li>
<li><a href="#rename_table">Renaming a Table</a></li>
<li><a href="#modifying_tables">Modifying a Table</a></li>
</ul>
<h2><a name="init"></a>Initializing the Forge Class</h2>
<p class="important"><strong>Important:</strong> In order to initialize the Forge class, your database driver must
already be running, since the forge class relies on it.</p>
<p>Load the Forge Class as follows:</p>
<code>$this->load->dbforge()</code>
<p>Once initialized you will access the functions using the <dfn>$this->dbforge</dfn> object:</p>
<code>$this->dbforge->some_function()</code>
<h2><a name="create"></a>$this->dbforge->create_database('db_name')</h2>
<p>Permits you to create the database specified in the first parameter. Returns TRUE/FALSE based on success or failure:</p>
<code>if ($this->dbforge->create_database('my_db'))<br />
{<br />
echo 'Database created!';<br />
}</code>
<h2><a name="drop"></a>$this->dbforge->drop_database('db_name')</h2>
<p>Permits you to drop the database specified in the first parameter. Returns TRUE/FALSE based on success or failure:</p>
<code>if ($this->dbforge->drop_database('my_db'))<br />
{<br />
echo 'Database deleted!';<br />
}</code>
<h1>Creating and Dropping Tables</h1>
<p>There are several things you may wish to do when creating tables. Add fields, add keys to the table, alter columns. CodeIgniter provides a mechanism for this.</p>
<h2><a name="add_field" id="add_field"></a>Adding fields</h2>
<p>Fields are created via an associative array. Within the array you must include a 'type' key that relates to the datatype of the field. For example, INT, VARCHAR, TEXT, etc. Many datatypes (for example VARCHAR) also require a 'constraint' key.</p>
<p><code>$fields = array(<br />
'users' => array(<br />
'type' => 'VARCHAR',<br />
'constraint' => '100',<br />
),<br />
);<br />
<br />
// will translate to "users VARCHAR(100)" when the field is added.</code></p>
<p>Additionally, the following key/values can be used:</p>
<ul>
<li>unsigned/true : to generate "UNSIGNED" in the field definition.</li>
<li>default/value : to generate a default value in the field definition.</li>
<li>null/true : to generate "NULL" in the field definition. Without this, the field will default to "NOT NULL".</li>
<li>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.</li>
</ul>
<p><code>$fields = array(<br />
'blog_id' => array(<br />
'type' => 'INT',<br />
'constraint' => 5, <br />
'unsigned' => TRUE,<br />
'auto_increment' => TRUE<br />
),<br />
'blog_title' => array(<br />
'type' => 'VARCHAR',<br />
'constraint' => '100',<br />
),<br />
'blog_author' => array(<br />
'type' =>'VARCHAR',<br />
'constraint' => '100',<br />
'default' => 'King of Town',<br />
),<br />
'blog_description' => array(<br />
'type' => 'TEXT',<br />
'null' => TRUE,<br />
),<br />
);<br />
</code></p>
<p>After the fields have been defined, they can be added using <dfn>$this->dbforge->add_field($fields);</dfn> followed by a call to the <dfn>create_table()</dfn> function.</p>
<h3>$this->dbforge->add_field()</h3>
<p>The add fields function will accept the above array.</p>
<h3>Passing strings as fields</h3>
<p>If you know exactly how you want a field to be created, you can pass the string into the field definitions with add_field()</p>
<p><code>$this->dbforge->add_field("label varchar(100) NOT NULL DEFAULT 'default label'");</code></p>
<p class="important">Note: Multiple calls to <dfn>add_field()</dfn> are cumulative.</p>
<h3>Creating an id field</h3>
<p>There is a special exception for creating id fields. A field with type id will automatically be assinged as an INT(9) auto_incrementing Primary Key.</p>
<p><code>$this->dbforge->add_field('id');<br />
// gives id INT(9) NOT NULL AUTO_INCREMENT</code></p>
<h2><a name="add_key" id="add_key"></a>Adding Keys</h2>
<p>Generally speaking, you'll want your table to have Keys. This is accomplished with <dfn>$this->dbforge->add_key('field')</dfn>. An optional second parameter set to TRUE will make it a primary key. Note that <dfn>add_key()</dfn> must be followed by a call to <dfn>create_table()</dfn>.</p>
<p>Multiple column non-primary keys must be sent as an array. Sample output below is for MySQL.</p>
<p><code>$this->dbforge->add_key('blog_id', TRUE);<br />
// gives PRIMARY KEY `blog_id` (`blog_id`)<br />
<br />
$this->dbforge->add_key('blog_id', TRUE);<br />
$this->dbforge->add_key('site_id', TRUE);<br />
// gives PRIMARY KEY `blog_id_site_id` (`blog_id`, `site_id`)<br />
<br />
$this->dbforge->add_key('blog_name');<br />
// gives KEY `blog_name` (`blog_name`)<br />
<br />
$this->dbforge->add_key(array('blog_name', 'blog_label'));<br />
// gives KEY `blog_name_blog_label` (`blog_name`, `blog_label`)</code></p>
<h2><a name="create_table" id="create_table"></a>Creating a table</h2>
<p>After fields and keys have been declared, you can create a new table with</p>
<p><code>$this->dbforge->create_table('table_name');<br />
// gives CREATE TABLE table_name</code></p>
<p>An optional second parameter set to TRUE adds an "IF NOT EXISTS" clause into the definition</p>
<p><code>$this->dbforge->create_table('table_name', TRUE);<br />
// gives CREATE TABLE IF NOT EXISTS table_name</code></p>
<h2><a name="drop_table" id="drop_table"></a>Dropping a table</h2>
<p>Executes a DROP TABLE sql</p>
<p><code>$this->dbforge->drop_table('table_name');<br />
// gives DROP TABLE IF EXISTS table_name</code></p>
<h2><a name="rename_table" id="rename_table"></a>Renaming a table</h2>
<p>Executes a TABLE rename</p>
<p><code>$this->dbforge->rename_table('old_table_name', 'new_table_name');<br />
// gives ALTER TABLE old_table_name RENAME TO new_table_name</code></p>
<h1><a name="modifying_tables" id="modifying_tables"></a>Modifying Tables</h1>
<h2>$this->dbforge->add_column()</h2>
<p>The add_column() function 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.</p>
<p><code>$fields = array(<br />
'preferences' => array('type' => 'TEXT')<br />
);<br />
$this->dbforge->add_column('table_name', $fields);<br />
<br />
// gives ALTER TABLE table_name ADD preferences TEXT</code></p>
<h2>$this->dbforge->drop_column()</h2>
<p>Used to remove a column from a table. </p>
<p><code>$this->dbforge->drop_column('table_name', 'column_to_drop');</code></p>
<h2>$this->dbforge->modify_column()</h2>
<p>The usage of this function is identical to add_column(), except it alters an existing column rather than adding a new one. In order to use it you must add a "name" key into the field defining array.</p>
<p><code>$fields = array(<br />
'old_name' => array(<br />
'name' => 'new_name',<br />
'type' => 'TEXT',<br />
),<br />
);<br />
$this->dbforge->modify_column('table_name', $fields);<br />
<br />
// gives ALTER TABLE table_name CHANGE old_name new_name TEXT </code></p>
<p> </p>
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