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POMySQL INNER JOIN - '=' vs 'like'
 

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  1. POMySQL INNER JOIN - '=' vs 'like'
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    <p>We're having some odd issues with MySQL inner joins. Basically, we get an odd error when using an '=' operator but using 'like' instead makes it work. Unfortunately, this is via ActiveRecord and no easy way to just slap 'like' in there instead, plus we want to understand what's actually happening here.</p> <p>Here is the query that fails:</p> <pre><code>mysql&gt; SELECT COUNT(*) FROM `versions` INNER JOIN `site_versions` ON `versions`.id = `site_versions`.version_id; </code></pre> <p>Here is the error:</p> <pre><code>ERROR 1296 (HY000): Got error 20008 'Query aborted due to out of query memory' from NDBCLUSTER </code></pre> <p>Here is the query that works:</p> <pre><code>mysql&gt; SELECT COUNT(*) FROM `versions` INNER JOIN `site_versions` ON `versions`.id like `site_versions`.version_id; </code></pre> <p>Here are some details on the tables themselves:</p> <pre><code>mysql&gt; desc site_versions; +----------------------+----------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +----------------------+----------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | | version_id | int(11) | YES | MUL | NULL | | [..snip..] +----------------------+----------+------+-----+---------+----------------+ mysql&gt; desc versions; +------------+--------------+------+-----+---------+----------------+ | Field | Type | Null | Key | Default | Extra | +------------+--------------+------+-----+---------+----------------+ | id | int(11) | NO | PRI | NULL | auto_increment | [..snip..] +------------+--------------+------+-----+---------+----------------+ </code></pre> <p>Any ideas why the 'like' works and the '=' does not?</p>
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    1. USJonathan Leffler
    1. USEric Anderson
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      1. POMySQL INNER JOIN - '=' vs 'like'
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      1. VTUpMod
    1. COis the like actually giving results you expect? maybe it's just failing to join anything (because what does like mean for ints?) and so avoiding the memory problem that the valid query is triggering.
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      1. USandrew cooke
    2. CO@andrewcooke - Hmm, `like` does seem to work when used that way: http://sqlfiddle.com/#!2/86792/1
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      1. USPaul Bellora
    3. COIt might also help the question to show the `explain` of each query.
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      1. USPaul Bellora
 

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