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active_record.html
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active_record.html
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<!DOCTYPE html PUBLIC "-//W3C//DTD XHTML 1.0 Transitional//EN" "http://www.w3.org/TR/xhtml1/DTD/xhtml1-transitional.dtd">
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<title>Active Record : CodeIgniter User Guide</title>
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<td><h1>CodeIgniter User Guide Version 2.0.3</h1></td>
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<a href="index.html">Database Library</a> ›
Active Record
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<h1>Active Record Class</h1>
<p>CodeIgniter uses a modified version of the Active Record Database Pattern.
This pattern allows information to be retrieved, inserted, and updated in your database with minimal scripting.
In some cases only one or two lines of code are necessary to perform a database action.
CodeIgniter does not require that each database table be its own class file. It instead provides a more simplified interface.</p>
<p>Beyond simplicity, a major benefit to using the Active Record features is that it allows you to create database independent applications, since the query syntax
is generated by each database adapter. It also allows for safer queries, since the values are escaped automatically by the system.</p>
<p class="important"><strong>Note:</strong> If you intend to write your own queries you can disable this class in your database config file, allowing the core database library and adapter to utilize fewer resources.<br /></p>
<ul>
<li><a href="#select">Selecting Data</a></li>
<li><a href="#insert">Inserting Data</a></li>
<li><a href="#update">Updating Data</a></li>
<li><a href="#delete">Deleting Data</a></li>
<li><a href="#chaining">Method Chaining</a></li>
<li><a href="#caching">Active Record Caching</a></li>
</ul>
<h1><a name="select"> </a>Selecting Data</h1>
<p>The following functions allow you to build SQL <strong>SELECT</strong> statements.</p>
<h2>$this->db->get();</h2>
<p>Runs the selection query and returns the result. Can be used by itself to retrieve all records from a table:</p>
<code>$query = $this->db->get('mytable');<br />
<br />
// Produces: SELECT * FROM mytable</code>
<p>The second and third parameters enable you to set a limit and offset clause:</p>
<code>$query = $this->db->get('mytable', 10, 20);<br />
<br />
// Produces: SELECT * FROM mytable LIMIT 20, 10 (in MySQL. Other databases have slightly different syntax)</code>
<p>You'll notice that the above function is assigned to a variable named <kbd>$query</kbd>, which can be used to show the results:</p>
<code>$query = $this->db->get('mytable');<br />
<br />
foreach ($query->result() as $row)<br />
{<br />
echo $row->title;<br />
}</code>
<p>Please visit the <a href="results.html">result functions</a> page for a full discussion regarding result generation.</p>
<h2>$this->db->get_where();</h2>
<p>Identical to the above function except that it permits you to add a "where" clause in the second parameter,
instead of using the db->where() function:</p>
<code>$query = $this->db->get_where('mytable', array('id' => $id), $limit, $offset);</code>
<p>Please read the about the where function below for more information.</p>
<p class="important">Note: get_where() was formerly known as getwhere(), which has been removed</p>
<h2>$this->db->select();</h2>
<p>Permits you to write the SELECT portion of your query:</p>
<p><code>
$this->db->select('title, content, date');<br />
<br />
$query = $this->db->get('mytable');<br />
<br />
// Produces: SELECT title, content, date FROM mytable</code></p>
<p class="important"><strong>Note:</strong> If you are selecting all (*) from a table you do not need to use this function. When omitted, CodeIgniter assumes you wish to SELECT *</p>
<p>$this->db->select() accepts an optional second parameter. If you set it to FALSE, CodeIgniter will not try to protect your field or table names with backticks. This is useful if you need a compound select statement.</p>
<p><code>$this->db->select('(SELECT SUM(payments.amount) FROM payments WHERE payments.invoice_id=4') AS amount_paid', FALSE); <br />
$query = $this->db->get('mytable');<br />
</code></p>
<h2>$this->db->select_max();</h2>
<p>Writes a "SELECT MAX(field)" portion for your query. You can optionally include a second parameter to rename the resulting field.</p>
<p><code>
$this->db->select_max('age');<br />
$query = $this->db->get('members');<br />
// Produces: SELECT MAX(age) as age FROM members<br />
<br />
$this->db->select_max('age', 'member_age');<br />
$query = $this->db->get('members');<br />
// Produces: SELECT MAX(age) as member_age FROM members</code></p>
<h2>$this->db->select_min();</h2>
<p>Writes a "SELECT MIN(field)" portion for your query. As with <dfn>select_max()</dfn>, You can optionally include a second parameter to rename the resulting field.</p>
<p><code>
$this->db->select_min('age');<br />
$query = $this->db->get('members');<br />
// Produces: SELECT MIN(age) as age FROM members</code></p>
<h2>$this->db->select_avg();</h2>
<p>Writes a "SELECT AVG(field)" portion for your query. As with <dfn>select_max()</dfn>, You can optionally include a second parameter to rename the resulting field.</p>
<p><code>
$this->db->select_avg('age');<br />
$query = $this->db->get('members');<br />
// Produces: SELECT AVG(age) as age FROM members</code></p>
<h2>$this->db->select_sum();</h2>
<p>Writes a "SELECT SUM(field)" portion for your query. As with <dfn>select_max()</dfn>, You can optionally include a second parameter to rename the resulting field.</p>
<p><code>
$this->db->select_sum('age');<br />
$query = $this->db->get('members');<br />
// Produces: SELECT SUM(age) as age FROM members</code></p>
<h2>$this->db->from();</h2>
<p>Permits you to write the FROM portion of your query:</p>
<code>
$this->db->select('title, content, date');<br />
$this->db->from('mytable');<br />
<br />
$query = $this->db->get();<br />
<br />
// Produces: SELECT title, content, date FROM mytable</code>
<p class="important">Note: As shown earlier, the FROM portion of your query can be specified in the <dfn>$this->db->get()</dfn> function, so use whichever method
you prefer.</p>
<h2>$this->db->join();</h2>
<p>Permits you to write the JOIN portion of your query:</p>
<code>
$this->db->select('*');<br />
$this->db->from('blogs');<br />
$this->db->join('comments', 'comments.id = blogs.id');<br />
<br />
$query = $this->db->get();<br />
<br />
// Produces: <br />
// SELECT * FROM blogs<br />
// JOIN comments ON comments.id = blogs.id<br />
</code>
<p>Multiple function calls can be made if you need several joins in one query.</p>
<p>If you need a specific type of JOIN you can specify it via the third parameter of the function.
Options are: left, right, outer, inner, left outer, and right outer.</p>
<code>
$this->db->join('comments', 'comments.id = blogs.id', <strong>'left'</strong>);<br />
<br />
// Produces: LEFT JOIN comments ON comments.id = blogs.id</code>
<h2>$this->db->where();</h2>
<p>This function enables you to set <strong>WHERE</strong> clauses using one of four methods:</p>
<p class="important"><strong>Note:</strong> All values passed to this function are escaped automatically, producing safer queries.</p>
<ol>
<li><strong>Simple key/value method:</strong>
<code>$this->db->where('name', $name);
<br /><br />// Produces: WHERE name = 'Joe' </code>
<p>Notice that the equal sign is added for you.</p>
<p>If you use multiple function calls they will be chained together with <var>AND</var> between them:</p>
<code>$this->db->where('name', $name);<br />
$this->db->where('title', $title);<br />
$this->db->where('status', $status);
<br /><br />// WHERE name = 'Joe' AND title = 'boss' AND status = 'active' </code> </li>
<li><strong>Custom key/value method:</strong>
<p>You can include an operator in the first parameter in order to control the comparison:</p>
<code>$this->db->where('name !=', $name);<br />
$this->db->where('id <', $id);
<br /><br />// Produces: WHERE name != 'Joe' AND id < 45 </code> </li>
<li><strong>Associative array method:</strong>
<code>
$array = array('name' => $name, 'title' => $title, 'status' => $status);<br /><br />
$this->db->where($array);
<br /><br />// Produces: WHERE name = 'Joe' AND title = 'boss' AND status = 'active' </code>
<p>You can include your own operators using this method as well:</p>
<code>
$array = array('name !=' => $name, 'id <' => $id, 'date >' => $date);<br /><br />
$this->db->where($array);</code> </li>
<li><strong>Custom string:</strong>
<p>You can write your own clauses manually:</p>
<code>
$where = "name='Joe' AND status='boss' OR status='active'";<br /><br />
$this->db->where($where);</code></li>
</ol>
<p>$this->db->where() accepts an optional third parameter. If you set it to FALSE, CodeIgniter will not try to protect your field or table names with backticks.</p>
<p><code> $this->db->where('MATCH (field) AGAINST ("value")', NULL, FALSE);<br />
</code></p>
<h2>$this->db->or_where();</h2>
<p>This function is identical to the one above, except that multiple instances are joined by OR:</p>
<code>
$this->db->where('name !=', $name);<br />
$this->db->or_where('id >', $id);
<br />
<br />// Produces: WHERE name != 'Joe' OR id > 50</code>
<p class="important">Note: or_where() was formerly known as orwhere(), which has been removed.</p>
<h2>$this->db->where_in();</h2>
<p>Generates a WHERE field IN ('item', 'item') SQL query joined with AND if appropriate</p>
<p><code>
$names = array('Frank', 'Todd', 'James');<br />
$this->db->where_in('username', $names);<br />
// Produces: WHERE username IN ('Frank', 'Todd', 'James')</code></p>
<h2>$this->db->or_where_in();</h2>
<p>Generates a WHERE field IN ('item', 'item') SQL query joined with OR if appropriate</p>
<p><code>
$names = array('Frank', 'Todd', 'James');<br />
$this->db->or_where_in('username', $names);<br />
// Produces: OR username IN ('Frank', 'Todd', 'James')</code></p>
<h2>$this->db->where_not_in();</h2>
<p>Generates a WHERE field NOT IN ('item', 'item') SQL query joined with AND if appropriate</p>
<p><code>
$names = array('Frank', 'Todd', 'James');<br />
$this->db->where_not_in('username', $names);<br />
// Produces: WHERE username NOT IN ('Frank', 'Todd', 'James')</code></p>
<h2>$this->db->or_where_not_in();</h2>
<p>Generates a WHERE field NOT IN ('item', 'item') SQL query joined with OR if appropriate</p>
<p><code>
$names = array('Frank', 'Todd', 'James');<br />
$this->db->or_where_not_in('username', $names);<br />
// Produces: OR username NOT IN ('Frank', 'Todd', 'James')</code></p>
<h2>$this->db->like();</h2>
<p>This function enables you to generate <strong>LIKE</strong> clauses, useful for doing searches.</p>
<p class="important"><strong>Note:</strong> All values passed to this function are escaped automatically.</p>
<ol>
<li><strong>Simple key/value method:</strong>
<code>$this->db->like('title', 'match');
<br /><br />// Produces: WHERE title LIKE '%match%' </code>
<p>If you use multiple function calls they will be chained together with <var>AND</var> between them:</p>
<code>$this->db->like('title', 'match');<br />
$this->db->like('body', 'match');
<br /><br />
// WHERE title LIKE '%match%' AND body LIKE '%match%</code>
If you want to control where the wildcard (%) is placed, you can use an optional third argument. Your options are 'before', 'after' and 'both' (which is the default).
<code>$this->db->like('title', 'match', 'before');
<br />
// Produces: WHERE title LIKE '%match' <br />
<br />
$this->db->like('title', 'match', 'after'); <br />
// Produces: WHERE title LIKE 'match%' <br />
<br />
$this->db->like('title', 'match', 'both'); <br />
// Produces: WHERE title LIKE '%match%' </code> </li>
If you do not want to use the wildcard (%) you can pass to the optional third argument the option 'none'.
<code>
$this->db->like('title', 'match', 'none'); <br />
// Produces: WHERE title LIKE 'match'
</code>
<li><strong>Associative array method:</strong>
<code>
$array = array('title' => $match, 'page1' => $match, 'page2' => $match);<br /><br />
$this->db->like($array);
<br /><br />// WHERE title LIKE '%match%' AND page1 LIKE '%match%' AND page2 LIKE '%match%'</code></li>
</ol>
<h2>$this->db->or_like();</h2>
<p>This function is identical to the one above, except that multiple instances are joined by OR:</p>
<code>
$this->db->like('title', 'match');<br />
$this->db->or_like('body', $match);
<br />
<br />// WHERE title LIKE '%match%' OR body LIKE '%match%'</code>
<p class="important">Note: or_like() was formerly known as orlike(), which has been removed.</p>
<h2>$this->db->not_like();</h2>
<p>This function is identical to <strong>like()</strong>, except that it generates NOT LIKE statements:</p>
<code> $this->db->not_like('title', 'match');<br />
<br />
// WHERE title NOT LIKE '%match%</code>
<h2>$this->db->or_not_like();</h2>
<p>This function is identical to <strong>not_like()</strong>, except that multiple instances are joined by OR:</p>
<code> $this->db->like('title', 'match');<br />
$this->db->or_not_like('body', 'match'); <br />
<br />
// WHERE title LIKE '%match% OR body NOT LIKE '%match%'</code>
<h2>$this->db->group_by();</h2>
<p>Permits you to write the GROUP BY portion of your query:</p>
<code>$this->db->group_by("title");
<br /><br />// Produces: GROUP BY title
</code>
<p>You can also pass an array of multiple values as well:</p>
<code>$this->db->group_by(array("title", "date"));
<br />
<br />// Produces: GROUP BY title, date</code>
<p class="important">Note: group_by() was formerly known as groupby(), which has been removed. </p>
<h2> $this->db->distinct();<br />
</h2>
<p>Adds the "DISTINCT" keyword to a query</p>
<p><code>$this->db->distinct();<br />
$this->db->get('table');<br />
<br />
// Produces: SELECT DISTINCT * FROM table</code></p>
<h2>$this->db->having();</h2>
<p>Permits you to write the HAVING portion of your query. There are 2 possible syntaxes, 1 argument or 2:</p>
<code>$this->db->having('user_id = 45');
<br />
// Produces: HAVING user_id = 45<br />
<br />
$this->db->having('user_id', 45); <br />
// Produces: HAVING user_id = 45<br />
<br />
</code>
<p>You can also pass an array of multiple values as well:</p>
<p><code>$this->db->having(array('title =' => 'My Title', 'id <' => $id)); <br />
<br />
// Produces: HAVING title = 'My Title', id < 45</code></p>
<p>If you are using a database that CodeIgniter escapes queries for, you can prevent escaping content by passing an optional third argument, and setting it to FALSE.</p>
<p><code>$this->db->having('user_id', 45); <br />
// Produces: HAVING `user_id` = 45 in some databases such as MySQL
<br />
$this->db->having('user_id', 45, FALSE); <br />
// Produces: HAVING user_id = 45</code></p>
<h2>$this->db->or_having();</h2>
<p>Identical to having(), only separates multiple clauses with "OR".</p>
<h2>$this->db->order_by();</h2>
<p>Lets you set an ORDER BY clause. The first parameter contains the name of the column you would like to order by.
The second parameter lets you set the direction of the result. Options are <kbd>asc</kbd> or <kbd>desc</kbd>, or <kbd>random</kbd>. </p>
<code>$this->db->order_by("title", "desc");
<br />
<br />// Produces: ORDER BY title DESC
</code>
<p>You can also pass your own string in the first parameter:</p>
<code>$this->db->order_by('title desc, name asc');
<br />
<br />// Produces: ORDER BY title DESC, name ASC
</code>
<p>Or multiple function calls can be made if you need multiple fields.</p>
<p><code>$this->db->order_by("title", "desc");<br />
$this->db->order_by("name", "asc"); <br />
<br />
// Produces: ORDER BY title DESC, name ASC
</code></p>
<p class="important">Note: order_by() was formerly known as orderby(), which has been removed.</p>
<p class="important">Note: random ordering is not currently supported in Oracle or MSSQL drivers. These will default to 'ASC'.</p>
<h2>$this->db->limit();</h2>
<p>Lets you limit the number of rows you would like returned by the query:</p>
<code>
$this->db->limit(10);<br />
<br />
// Produces: LIMIT 10</code>
<p>The second parameter lets you set a result offset.</p>
<code>
$this->db->limit(10, 20);<br />
<br />
// Produces: LIMIT 20, 10 (in MySQL. Other databases have slightly different syntax)</code>
<h2>$this->db->count_all_results();</h2>
<p>Permits you to determine the number of rows in a particular Active Record query. Queries will accept Active Record restrictors such as where(), or_where(), like(), or_like(), etc. Example:</p>
<code>echo $this->db->count_all_results('<var>my_table</var>');<br />
// Produces an integer, like 25<br />
<br />
$this->db->like('title', 'match');<br />
$this->db->from('<var>my_table</var>');<br />
echo $this->db->count_all_results();<br />
// Produces an integer, like 17 </code>
<h2>$this->db->count_all();</h2>
<p>Permits you to determine the number of rows in a particular table. Submit the table name in the first parameter. Example:</p>
<code>echo $this->db->count_all('<var>my_table</var>');<br />
<br />
// Produces an integer, like 25</code>
<a name="insert"> </a>
<h1>Inserting Data</h1>
<h2>$this->db->insert();</h2>
<p>Generates an insert string based on the data you supply, and runs the query. You can either pass an
<strong>array</strong> or an <strong>object</strong> to the function. Here is an example using an array:</p>
<code>
$data = array(<br />
'title' => 'My title' ,<br />
'name' => 'My Name' ,<br />
'date' => 'My date'<br />
);<br />
<br />
$this->db->insert('mytable', $data);
<br /><br />
// Produces: INSERT INTO mytable (title, name, date) VALUES ('My title', 'My name', 'My date')</code>
<p>The first parameter will contain the table name, the second is an associative array of values.</p>
<p>Here is an example using an object:</p>
<code>
/*<br />
class Myclass {<br />
var $title = 'My Title';<br />
var $content = 'My Content';<br />
var $date = 'My Date';<br />
}<br />
*/<br />
<br />
$object = new Myclass;<br />
<br />
$this->db->insert('mytable', $object);
<br /><br />
// Produces: INSERT INTO mytable (title, content, date) VALUES ('My Title', 'My Content', 'My Date')</code>
<p>The first parameter will contain the table name, the second is an object.</p>
<p class="important"><strong>Note:</strong> All values are escaped automatically producing safer queries.</p>
<h2>$this->db->insert_batch();</h2>
<p>Generates an insert string based on the data you supply, and runs the query. You can either pass an
<strong>array</strong> or an <strong>object</strong> to the function. Here is an example using an array:</p>
<code>
$data = array(<br/>
array(<br />
'title' => 'My title' ,<br />
'name' => 'My Name' ,<br />
'date' => 'My date'<br />
),<br />
array(<br />
'title' => 'Another title' ,<br />
'name' => 'Another Name' ,<br />
'date' => 'Another date'<br />
)<br/>
);<br />
<br />
$this->db->update_batch('mytable', $data);
<br /><br />
// Produces: INSERT INTO mytable (title, name, date) VALUES ('My title', 'My name', 'My date'), ('Another title', 'Another name', 'Another date')</code>
<p>The first parameter will contain the table name, the second is an associative array of values.</p>
<p class="important"><strong>Note:</strong> All values are escaped automatically producing safer queries.</p>
<h2>$this->db->set();</h2>
<p>This function enables you to set values for <dfn>inserts</dfn> or <dfn>updates</dfn>.</p>
<p><strong>It can be used instead of passing a data array directly to the insert or update functions:</strong> </p>
<code>$this->db->set('name', $name);
<br />
$this->db->insert('mytable');
<br /><br />
// Produces: INSERT INTO mytable (name) VALUES ('{$name}')</code>
<p>If you use multiple function called they will be assembled properly based on whether you are doing an insert or an update:</p>
<code>$this->db->set('name', $name);<br />
$this->db->set('title', $title);<br />
$this->db->set('status', $status);<br />
$this->db->insert('mytable'); </code>
<p><strong>set()</strong> will also accept an optional third parameter ($escape), that will prevent data from being escaped if set to FALSE. To illustrate the difference, here is set() used both with and without the escape parameter.</p>
<p><code>$this->db->set('field', 'field+1', FALSE);<br />
$this->db->insert('mytable'); <br />
// gives INSERT INTO mytable (field) VALUES (field+1)<br />
<br />
$this->db->set('field', 'field+1');<br />
$this->db->insert('mytable'); <br />
// gives INSERT INTO mytable (field) VALUES ('field+1')</code></p>
<p>You can also pass an associative array to this function:</p>
<code>
$array = array('name' => $name, 'title' => $title, 'status' => $status);<br /><br />
$this->db->set($array);<br />
$this->db->insert('mytable');
</code>
<p>Or an object:</p>
<code>
/*<br />
class Myclass {<br />
var $title = 'My Title';<br />
var $content = 'My Content';<br />
var $date = 'My Date';<br />
}<br />
*/<br />
<br />
$object = new Myclass;<br />
<br />
$this->db->set($object);<br />
$this->db->insert('mytable');
</code>
<a name="update"> </a>
<h1>Updating Data</h1>
<h2>$this->db->update();</h2>
<p>Generates an update string and runs the query based on the data you supply. You can pass an
<strong>array</strong> or an <strong>object</strong> to the function. Here is an example using
an array:</p>
<code>
$data = array(<br />
'title' => $title,<br />
'name' => $name,<br />
'date' => $date<br />
);<br />
<br />
$this->db->where('id', $id);<br />
$this->db->update('mytable', $data);
<br /><br />
// Produces:<br />
// UPDATE mytable <br />
// SET title = '{$title}', name = '{$name}', date = '{$date}'<br />
// WHERE id = $id</code>
<p>Or you can supply an object:</p>
<code>
/*<br />
class Myclass {<br />
var $title = 'My Title';<br />
var $content = 'My Content';<br />
var $date = 'My Date';<br />
}<br />
*/<br />
<br />
$object = new Myclass;<br />
<br />
$this->db->where('id', $id);<br />
$this->db->update('mytable', $object);
<br />
<br />
// Produces:<br />
// UPDATE mytable <br />
// SET title = '{$title}', name = '{$name}', date = '{$date}'<br />
// WHERE id = $id</code>
<p class="important"><strong>Note:</strong> All values are escaped automatically producing safer queries.</p>
<p>You'll notice the use of the <dfn>$this->db->where()</dfn> function, enabling you to set the WHERE clause.
You can optionally pass this information directly into the update function as a string:</p>
<code>$this->db->update('mytable', $data, "id = 4");</code>
<p>Or as an array:</p>
<code>$this->db->update('mytable', $data, array('id' => $id));</code>
<p>You may also use the <dfn>$this->db->set()</dfn> function described above when performing updates.</p>
<a name="delete"> </a>
<h1>Deleting Data</h1>
<h2>$this->db->delete();</h2>
<p>Generates a delete SQL string and runs the query.</p>
<code>
$this->db->delete('mytable', array('id' => $id));
<br /><br />
// Produces:<br />
// DELETE FROM mytable <br />
// WHERE id = $id</code>
<p>The first parameter is the table name, the second is the where clause. You can also use the <dfn>where()</dfn> or <dfn>or_where()</dfn> functions instead of passing
the data to the second parameter of the function:</p>
<p><code> $this->db->where('id', $id);<br />
$this->db->delete('mytable'); <br />
<br />
// Produces:<br />
// DELETE FROM mytable <br />
// WHERE id = $id</code></p>
<p>An array of table names can be passed into delete() if you would like to delete data from more than 1 table.</p>
<p><code>$tables = array('table1', 'table2', 'table3');<br />
$this->db->where('id', '5');<br />
$this->db->delete($tables);</code></p>
<p>If you want to delete all data from a table, you can use the <dfn>truncate()</dfn> function, or <dfn>empty_table()</dfn>.</p>
<h2>$this->db->empty_table();</h2>
<p>Generates a delete SQL string and runs the query.<code> $this->db->empty_table('mytable'); <br />
<br />
// Produces<br />
// DELETE FROM mytable</code></p>
<h2>$this->db->truncate();</h2>
<p>Generates a truncate SQL string and runs the query.</p>
<code> $this->db->from('mytable'); <br />
$this->db->truncate(); <br />
// or <br />
$this->db->truncate('mytable'); <br />
<br />
// Produce:<br />
// TRUNCATE mytable <br />
</code>
<p class="important"><strong>Note:</strong> If the TRUNCATE command isn't available, truncate() will execute as "DELETE FROM table".</p>
<h1><a name="chaining"> </a>Method Chaining</h1>
<p>Method chaining allows you to simplify your syntax by connecting multiple functions. Consider this example:</p>
<code>
<dfn>$this->db</dfn><kbd>-></kbd><var>select</var>('title')<kbd>-></kbd><var>from</var>('mytable')<kbd>-></kbd><var>where</var>('id', $id)<kbd>-></kbd><var>limit</var>(10, 20);<br />
<br />
$query = $this->db->get();</code>
<p class="important"><strong>Note:</strong> Method chaining only works with PHP 5.</p>
<p> </p>
<h1><a name="caching"> </a>Active Record Caching</h1>
<p>While not "true" caching, Active Record enables you to save (or "cache") certain parts of your queries for reuse at a later point in your script's execution. Normally, when an Active Record call is completed, all stored information is reset for the next call. With caching, you can prevent this reset, and reuse information easily.</p>
<p>Cached calls are cumulative. If you make 2 cached select() calls, and then 2 uncached select() calls, this will result in 4 select() calls. There are three Caching functions available:</p>
<h2>$this->db->start_cache()</h2>
<p>This function must be called to begin caching. All Active Record queries of the correct type (see below for supported queries) are stored for later use.</p>
<h2>$this->db->stop_cache()</h2>
<p>This function can be called to stop caching.</p>
<h2>$this->db->flush_cache()</h2>
<p>This function deletes all items from the Active Record cache.</p>
<p>Here's a usage example:</p>
<p><code>$this->db->start_cache();<br />
$this->db->select('field1');<br />
$this->db->stop_cache();<br /><br />
$this->db->get('tablename');<br />
<br />
//Generates: SELECT `field1` FROM (`tablename`)<br />
<br />
$this->db->select('field2');<br />
$this->db->get('tablename');<br />
<br />
//Generates: SELECT `field1`, `field2` FROM (`tablename`)<br />
<br />
$this->db->flush_cache();<br />
<br />
$this->db->select('field2');<br />
$this->db->get('tablename');<br />
<br />
//Generates: SELECT `field2` FROM (`tablename`)</code></p>
<p class="important"> <strong>Note:</strong> The following statements can be cached: select, from, join, where, like, group_by, having, order_by, set</p>
<p> </p>
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