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POMySQL: order by and limit gives wrong result
 

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  1. POMySQL: order by and limit gives wrong result
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    <p>MySQL ver 5.1.26</p> <p>I'm getting the wrong result with a select that has where, order by and limit clauses. It's only a problem when the order by uses the id column.</p> <p>I saw the MySQL manual for <a href="http://dev.mysql.com/doc/refman/5.0/en/limit-optimization.html" rel="nofollow noreferrer">LIMIT Optimization</a></p> <p>My guess from reading the manual is that there is some problem with the index on the primary key, id. But I don't know where I should go from here...</p> <p><strong>Question: what should I do to best solve the problem?</strong></p> <pre><code>Works correctly: mysql&gt; SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY id DESC ; +------+---------------------+ | id | created_at | +------+---------------------+ | 1336 | 2010-05-14 08:05:25 | | 1334 | 2010-05-06 08:05:25 | | 1331 | 2010-05-05 23:18:11 | +------+---------------------+ 3 rows in set (0.00 sec) WRONG result when limit added! Should be the first row, id - 1336 mysql&gt; SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY id DESC limit 1; +------+---------------------+ | id | created_at | +------+---------------------+ | 1331 | 2010-05-05 23:18:11 | +------+---------------------+ 1 row in set (0.00 sec) Works correctly: mysql&gt; SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY created_at DESC ; +------+---------------------+ | id | created_at | +------+---------------------+ | 1336 | 2010-05-14 08:05:25 | | 1334 | 2010-05-06 08:05:25 | | 1331 | 2010-05-05 23:18:11 | +------+---------------------+ 3 rows in set (0.01 sec) Works correctly with limit: mysql&gt; SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY created_at DESC limit 1; +------+---------------------+ | id | created_at | +------+---------------------+ | 1336 | 2010-05-14 08:05:25 | +------+---------------------+ 1 row in set (0.01 sec) Additional info: explain SELECT id, created_at FROM billing_invoices WHERE (billing_invoices.account_id = 5) ORDER BY id DESC limit 1; +----+-------------+------------------+-------+--------------------------------------+--------------------------------------+---------+------+------+-------------+ | id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra | +----+-------------+------------------+-------+--------------------------------------+--------------------------------------+---------+------+------+-------------+ | 1 | SIMPLE | billing_invoices | range | index_billing_invoices_on_account_id | index_billing_invoices_on_account_id | 4 | NULL | 3 | Using where | +----+-------------+------------------+-------+--------------------------------------+--------------------------------------+---------+------+------+-------------+ </code></pre> <p>Added SHOW CREATE TABLE billing_invoices result:</p> <pre><code>Table -- billing_invoices Create Table -- CREATE TABLE `billing_invoices` ( `id` int(11) NOT NULL AUTO_INCREMENT, `account_id` int(11) NOT NULL, `invoice_date` date NOT NULL, `prior_invoice_id` int(11) DEFAULT NULL, `closing_balance` decimal(8,2) NOT NULL, `note` varchar(255) COLLATE utf8_unicode_ci DEFAULT NULL, `monthly_invoice` tinyint(1) NOT NULL, `created_at` datetime DEFAULT NULL, `updated_at` datetime DEFAULT NULL, PRIMARY KEY (`id`), KEY `index_billing_invoices_on_account_id` (`account_id`) ) ENGINE=InnoDB AUTO_INCREMENT=1337 DEFAULT CHARSET=utf8 COLLATE=utf8_unicode_ci </code></pre> <p>Added more:</p> <p>I now see that on my development machine, everything is working correctly. That machine has version VERSION() of 5.1.26-rc-log </p> <p>On my <em>production</em> machine, where the problem is, I see that VERSION() returns 5.1.26-rc-percona-log</p> <p>So at this point, I'm thinking the problem is with the percona software?</p> <p>Added more:</p> <p>At this point, I'm going to consider it a bug in the Percona InnoDB driver. I've put a <a href="http://forum.percona.com/index.php/t/1446/" rel="nofollow noreferrer">question to their forum</a>. As an immediate work-around, I'm going to order by created_at. I will also investigate upgrading the db on my system and see if that helps.</p> <p>My thanks to Rabbott and mdma for their help. I also appreciate the help that I'm not doing something silly, this really is a problem.</p>
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    1. USLarry K
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    1. COPlease include the results of the following query in your question: `SHOW CREATE TABLE billing_invoices;`.
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      1. USAsaph
    2. COVery strange. I tested a similar query on my mysql server and it works just find when i use order by primary_id DESC limit 1 ... my primary id is a autogenerated int... seems like a bug on your server...
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      1. USVidar Vestnes
 

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