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+<a href="http://codeigniter.com/">CodeIgniter Home</a> ›
+<a href="../index.html">User Guide Home</a> ›
+<a href="index.html">Database Library</a> ›
+Transactions
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+
+
+<h1>Transactions</h1>
+
+<p>CodeIgniter's database abstraction allows you to use <dfn>transactions</dfn> with databases that support transaction-safe table types. In MySQL, you'll need
+to be running InnoDB or BDB table types rather than the more common MyISAM. Most other database platforms support transactions natively.</p>
+
+<p>If you are not familiar with
+transactions we recommend you find a good online resource to learn about them for your particular database. The information below assumes you
+have a basic understanding of transactions.
+</p>
+
+<h2>CodeIgniter's Approach to Transactions</h2>
+
+<p>CodeIgniter utilizes an approach to transactions that is very similar to the process used by the popular database class ADODB. We've chosen that approach
+because it greatly simplifies the process of running transactions. In most cases all that is required are two lines of code.</p>
+
+<p>Traditionally, transactions have required a fair amount of work to implement since they demand that you to keep track of your queries
+and determine whether to <dfn>commit</dfn> or <dfn>rollback</dfn> based on the success or failure of your queries. This is particularly cumbersome with
+nested queries. In contrast,
+we've implemented a smart transaction system that does all this for you automatically (you can also manage your transactions manually if you choose to,
+but there's really no benefit).</p>
+
+<h2>Running Transactions</h2>
+
+<p>To run your queries using transactions you will use the <dfn>$this->db->trans_start()</dfn> and <dfn>$this->db->trans_complete()</dfn> functions as follows:</p>
+
+<code>
+<kbd>$this->db->trans_start();</kbd><br />
+$this->db->query('AN SQL QUERY...');<br />
+$this->db->query('ANOTHER QUERY...');<br />
+$this->db->query('AND YET ANOTHER QUERY...');<br />
+<kbd>$this->db->trans_complete();</kbd>
+</code>
+
+<p>You can run as many queries as you want between the start/complete functions and they will all be committed or rolled back based on success or failure
+of any given query.</p>
+
+
+<h2>Strict Mode</h2>
+
+<p>By default CodeIgniter runs all transactions in <dfn>Strict Mode</dfn>. When strict mode is enabled, if you are running multiple groups of
+transactions, if one group fails all groups will be rolled back. If strict mode is disabled, each group is treated independently, meaning
+a failure of one group will not affect any others.</p>
+
+<p>Strict Mode can be disabled as follows:</p>
+
+<code>$this->db->trans_strict(FALSE);</code>
+
+
+<h2>Managing Errors</h2>
+
+<p>If you have error reporting enabled in your <dfn>config/database.php</dfn> file you'll see a standard error message if the commit was unsuccessful. If debugging is turned off, you can
+manage your own errors like this:</p>
+
+<code>
+$this->db->trans_start();<br />
+$this->db->query('AN SQL QUERY...');<br />
+$this->db->query('ANOTHER QUERY...');<br />
+$this->db->trans_complete();<br />
+<br />
+if (<kbd>$this->db->trans_status()</kbd> === FALSE)<br />
+{<br />
+ // generate an error... or use the log_message() function to log your error<br />
+}
+</code>
+
+
+<h2>Enabling Transactions</h2>
+
+<p>Transactions are enabled automatically the moment you use <dfn>$this->db->trans_start()</dfn>. If you would like to disable transactions you
+can do so using <dfn>$this->db->trans_off()</dfn>:</p>
+
+<code>
+<kbd>$this->db->trans_off()</kbd><br /><br />
+
+$this->db->trans_start();<br />
+$this->db->query('AN SQL QUERY...');<br />
+$this->db->trans_complete();
+</code>
+
+<p class="important">When transactions are disabled, your queries will be auto-commited, just as they are when running queries without transactions.</p>
+
+
+<h2>Test Mode</h2>
+
+<p>You can optionally put the transaction system into "test mode", which will cause your queries to be rolled back -- even if the queries produce a valid result.
+To use test mode simply set the first parameter in the <dfn>$this->db->trans_start()</dfn> function to <samp>TRUE</samp>:</p>
+
+<code>
+$this->db->trans_start(<samp>TRUE</samp>); // Query will be rolled back<br />
+$this->db->query('AN SQL QUERY...');<br />
+$this->db->trans_complete();
+</code>
+
+
+<h2>Running Transactions Manually</h2>
+
+<p>If you would like to run transactions manually you can do so as follows:</p>
+
+<code>
+$this->db->trans_begin();<br /><br />
+
+$this->db->query('AN SQL QUERY...');<br />
+$this->db->query('ANOTHER QUERY...');<br />
+$this->db->query('AND YET ANOTHER QUERY...');<br />
+
+<br />
+
+if ($this->db->trans_status() === FALSE)<br />
+{<br />
+ $this->db->trans_rollback();<br />
+}<br />
+else<br />
+{<br />
+ $this->db->trans_commit();<br />
+}<br />
+</code>
+
+<p class="important"><strong>Note:</strong> Make sure to use <kbd>$this->db->trans_begin()</kbd> when running manual transactions, <strong>NOT</strong>
+<dfn>$this->db->trans_start()</dfn>.</p>
+
+
+
+
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