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Blastrix
Posting Yak Master
208 Posts |
 Posted - 2003-11-06 : 13:15:41
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| If I have an IF statement such as:IF (@ID > 0 And EXISTS(Select * From SomeTable Where ID = @ID))Will the whole statement always be evaluated, or will SQL stop evaluating if @ID is 0 or less?Thanks,Steve |
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robvolk
Most Valuable Yak
15732 Posts |
Posted - 2003-11-06 : 13:28:42
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| I believe SQL Server performs the short-circuit evaluation and will stop processing after it determines the expression is true. I can't remember where I read that though, but Inside SQL Server was probably it. I'd recommend writing your IF statements to take advantage of it, I do that with mine. It can't hurt. |
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jsmith8858
Dr. Cross Join
7423 Posts |
Posted - 2003-11-06 : 13:45:42
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| you know the trick how to test:if (1=1 or (1/0)=0) print 'ok'if it prints OK, it is short-circuiting. To save the suspense, i ran this and it printed OK, so it isn't evaluating any more than it needs to."Case" does the same thing:select case when 1=1 then 1 else 2/0 endthat works fine.Finally, what about WHERE clauses:select 1 where 1=1 or 1/0 = 0works fine as well !- Jeff |
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How are IF statements handled?