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POHow do you perform an AND with a join?
 

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  1. POHow do you perform an AND with a join?
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    <p>I have the following data structure and data:</p> <pre><code>CREATE TABLE `parent` ( `id` int(11) NOT NULL auto_increment, `name` varchar(10) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `parent` VALUES(1, 'parent 1'); INSERT INTO `parent` VALUES(2, 'parent 2'); CREATE TABLE `other` ( `id` int(11) NOT NULL auto_increment, `name` varchar(10) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `other` VALUES(1, 'other 1'); INSERT INTO `other` VALUES(2, 'other 2'); CREATE TABLE `relationship` ( `id` int(11) NOT NULL auto_increment, `parent_id` int(11) NOT NULL, `other_id` int(11) NOT NULL, PRIMARY KEY (`id`) ) ENGINE=MyISAM DEFAULT CHARSET=latin1; INSERT INTO `relationship` VALUES(1, 1, 1); INSERT INTO `relationship` VALUES(2, 1, 2); INSERT INTO `relationship` VALUES(3, 2, 1); </code></pre> <p>I want to find the the parent records with both other's 1 &amp; 2.</p> <p>This is what I've figured out, but I'm wondering if there is a better way:</p> <pre><code>SELECT p.id, p.name FROM parent AS p LEFT JOIN relationship AS r1 ON (r1.parent_id = p.id) LEFT JOIN relationship AS r2 ON (r2.parent_id = p.id) WHERE r1.other_id = 1 AND r2.other_id = 2; </code></pre> <p>The result is 1, "parent 1" which is correct. The problem is that once you get a list of 5+ joins, it gets messy and as the relationship table grows, it gets slow.</p> <p>Is there a better way?</p> <p>I'm using MySQL and PHP, but this is probably pretty generic.</p>
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