order of SQL execution

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order of SQL execution

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Ramesh Lende

Posted Friday, February 08, 2008 8:09 AM

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Last Login: Friday, June 03, 2011 9:11 AM
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I have a query

Select * from Table1 where
Filter1>100 and Filter2= "test" and filter3< 100

Can anyone tell me how would this query executed?

Will Filter1 will be filtered first or filter 3? Reason i want to know is because if filter1 is getting executed first then
i would put that filter which would reduce more number of records.

Same question i have for "OR" condition

Select * from Table1 where
Filter1>100 or Filter2= "test" or filter3< 100

Thanks,
Ramesh.

Post #453261

Steve Jones - SSC Editor

Posted Friday, February 08, 2008 8:16 AM

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You can view the execution plan in SSMS for the query and see the order in which things are applied. The short answer is "it depends". The optimizer will consider # of records, based on statistics, and indexes and it could do either one first.

The way you write it is irrelevant.

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Post #453268

Vijaya Kadiyala

Posted Friday, February 08, 2008 12:00 PM

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Hi,
the order of the where condtions doesn't play interms which one to execute first. It depends on the columns which you are using in where condition has indexes or not.
Thanks -- Vj
http://dotnetvj.blogspot.com

Thanks -- Vijaya Kadiyala
www.dotnetvj.com
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Post #453403

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