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POSQL query to find matches for multiple criteria
 

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    <p>If I had a <code>PERMISSIONS</code> table that looked like this:</p> <pre><code>PERSON PERMISSION ------ ---------- Bob red John red John blue Mary red Mary blue Mary yellow </code></pre> <p>and a THINGS table that looks like this:</p> <pre><code>THING PERMISSION ----- ---------- apple red eggplant red eggplant blue </code></pre> <p>I'm trying to come up with a pure SQL query that would let me find out what <code>PERSON</code>s have access to what <code>THING</code>s. Basically, I want a query that would look something like:</p> <pre><code>SELECT person FROM ... vague handwaving here ... WHERE thing = 'eggplant' </code></pre> <p>and have it return "John" and "Mary". The key point being the number of permissions necessary for access to the thing is arbitrary.</p> <p>I feel like this should be obvious, but I just can't come up with an elegant solution. Oracle compatible solutions preferred.</p> <p>Edit:</p> <p>Solutions from Kosta and JBrooks work well. Below is a modified version of Kosta's solution that only hits the indexes twice, as opposed to 3x for Kosta's and 4x for JBrooks's (though I agree with JBrooks that this is probably unnecessary optimization).</p> <pre><code>SELECT p.person, num_permission, COUNT(p.person) FROM permissions p INNER JOIN ( SELECT permission, COUNT(1) OVER (PARTITION BY thing) AS num_permission FROM things WHERE thing = 'eggplant' ) t ON t.permission = p.permission GROUP BY p.person, num_permission HAVING COUNT(p.person) = num_permission </code></pre>
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    1. COI'm no Oracle expert, but I might be able to offer some handwaving assistance. For any given person, if "the distinct count of their permissions for a particular thing" equals "the distinct count of permissions required for that thing" then they can access that thing. If (PERSON, PERMISSION) and (THING, PERMISSION) are primary keys on the two tables then you can forget about the distinct aspect.
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