April 25, 2008 at 12:52 pm
I read somewhere at some time that it's best to put your most-likely-to-fail comparison towards the 'front' so if it returns false, for an AND statement, the whole thing is false right away. I can't remember the direction of processing for comparison statements
eg.
...
WHERE T1.a = T2.a AND T1.b = T2.b
which would process first, T1.a = T2.a or T1.b = T2.b?
Thanks
P.S. I tried to google this but "order" and "left" or "right" pulls back a ton of stuff about SQL
April 25, 2008 at 1:12 pm
Thanks much!
April 25, 2008 at 2:48 pm
There isn't a guaranteed sequence. SQL Server will decide how to resolve the query, and which sequence to apply Where statements in, based on how much work it thinks will be involved.
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