Why does "non exists" SQL query work and "not in" doesn't

Posted by Josh on Stack Overflow See other posts from Stack Overflow or by Josh
Published on 2010-04-02T17:34:05Z Indexed on 2010/04/02 17:53 UTC
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sql

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tsql

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sql-server-2008

I spent some time trying to figure out why this query isn't pulling the results i expected:

SELECT * FROM NGS WHERE ESPSSN NOT IN (SELECT SSN FROM CENSUS)

finally i tried writing the query another way and this ended up getting the expected results:

SELECT * FROM NGS n WHERE NOT EXISTS (SELECT * FROM CENSUS WHERE SSN = n.ESPSSN)

The first query seems more appropriate and "correct". I use "in" and "not in" all the time for similar selects and have never had a problem that i know of.

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