which one is better in or exists

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which one is better in or exists

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Topic

msrs

32 Posts

Posted - 2007-12-06 : 01:36:11

Dear all,
i am trying to improve the performance of stored procedures and functions in that in key word is there i have to replace with exists.which one will give better performance.

Thanks&Regards,

Msrs

SwePeso
Patron Saint of Lost Yaks

30421 Posts

Posted - 2007-12-06 : 03:24:45

Most often exists will perform better.

E 12°55'05.25"
N 56°04'39.16"

LoztInSpace
Aged Yak Warrior

940 Posts

Posted - 2007-12-06 : 17:59:14

They behave differently around NULLs so it is not necessarily a search & replace operation. You should check each query. Consider:

select * from
(select '1' a union select '2' union select '3' union select null ) t1
where
exists
(select a from
(select '1' a union select '2' union select '3' union select null) t2 )
vs
select * from
(select '1' a union select '2' union select '3' union select null ) t1
where
a in
(select a from
(select '1' a union select '2' union select '3' union select null) t2 )

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