does a record exist? count vs limit vs both nested

Question

say you want to check if any rows match a query (just a true/false if the table contains any matches). which is preferred (and optionally, why)? or is there a better way?

SELECT COUNT(*) > 0 FROM someTable WHERE someField = someValue

or

SELECT someField = someValue FROM someTable WHERE someField = someValue LIMIT 1

or

SELECT COUNT(*) > 0 FROM (SELECT someValue FROM someTable WHERE someField = someValue LIMIT 1) someAlias;

stackoverflow.com/questions/4484974/…

ethrbunny
– ethrbunny

2012-12-15 16:04:37 +00:00
Commented Dec 15, 2012 at 16:04 — ethrbunny
– ethrbunny, Commented Dec 15, 2012 at 16:04

Jeff H · Accepted Answer · 2012-12-16 19:40:46Z

I would use EXISTS:

SELECT EXISTS (SELECT * FROM someTable);

This returns 1 (True) if the subquery returns any rows at all, otherwise it returns 0 (False).

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