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Editorial Team
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Asked: 2026-05-27T17:31:55+00:00

I join table A to table B and need to know if table B

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I join table A to table B and need to know if table B has 1 matching row or more than one.

Of course, I can do it with GROUP BY and COUNT, but it’s an overkill, because it has to count all the matches and I don’t need this info.

Is there a simple way to get the info I need (only one matching row or more) which short circuits the evaluation and stops when it knows the answer without scanning and counting all the remaining matches?

Or should I not care about this, becasue it’s not a big performance hit and I should simply go with COUNT?

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1 Answer

  1. Editorial Team

    It really depends on the size of the DB, and your exact requirements. Generally a count()/Group By/Having combination is a pretty efficient query, with the right indexes. You could do it in a more complicated way, for example, having a trigger on after update that keeps a count table updated.

    Are you seeing the count(*)/group/having combination giving you performance issues?

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