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    <p>I assume that the natrual key of this table is document_id + subject_id, and that id is a surrogate; IOW, document_id and subject_id are unique. As such, I'm just going to pretend it doesn't exist and that a unique constraint is on the natural key.</p> <p>Let's start with the obvious.</p> <pre><code>SELECT document_id, subject_id FROM document_subjects WHERE subject_id IN (17,76) </code></pre> <p>That gets you everything you want <em>plus</em> stuff you don't want. So all we need to do is filter out the other stuff. The "other stuff" is groups of rows having a count that is not equal to the count of the desired subjects.</p> <pre><code>SELECT document_id FROM document_subjects WHERE subject_id IN (17,76) GROUP BY document_id HAVING COUNT(*) = 2 </code></pre> <p>Note that subject_id is removed because it doesn't participate in grouping. Taking this one step further, i'm going to add an imaginary table called subjects_i_want that contains N rows of subjects you want.</p> <pre><code>SELECT document_id FROM document_subjects WHERE subject_id IN (SELECT subject_id FROM subjects_i_want) GROUP BY document_id HAVING COUNT(*) = (SELECT COUNT(*) FROM subjects_i_want) </code></pre> <p>Obviously subjects_i_want could be swapped out for another subquery, temporary table, or whatever. But, once you have this list of document_id, you can use it within a subselect of a bigger query. </p> <pre><code>SELECT document_id, subject_id, ... FROM document_subjects WHERE document_id IN( SELECT document_id FROM document_subjects WHERE subject_id IN (SELECT subject_id FROM subjects_i_want) GROUP BY document_id HAVING COUNT(*) = (SELECT COUNT(*) FROM subjects_i_want)) </code></pre> <p>Or whatever.</p>
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    1. USAlex Papadimoulis
    1. USAlex Papadimoulis
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    1. COAwesome, thanks.
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      1. USMaciek
    2. CO+1 very nice, Alex. I've noticed a few variations of this question lately, and this is the most clearly presented general solution I've seen so far.
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      1. USMatt
 

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