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IN and EXISTS


IN and EXISTS

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vxhughes
vxhughes
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I’m trying to really understand the difference between IN and EXISTS. Would the following be fair statements?

IN
• first evaluates: inner query
• evaluates outer query until: every row in outer query's table examined
• accepts as argument: a list of literal values or a condition (most often used when argument is a list of literal values)
• is faster when inner query's table contains: few records / values
• is usually: slower

EXISTS
• first evaluates: outer query
• evaluates outer query until: inner query finds a record that satifies condition
(if inner query doesn't find any records that satify condition: until every row in outer query's table examined)
• accepts as argument: a condition
• is faster when inner query's table contains: many records
• is usually: faster
GilaMonster
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No, not at all.

They're two ways of stating the same thing, they perform and execute identically.

Gail Shaw
Microsoft Certified Master: SQL Server, MVP, M.Sc (Comp Sci)
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mister.magoo
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GilaMonster (6/20/2013)
No, not at all.

They're two ways of stating the same thing, they perform and execute identically.


Isn't it true to say that they can be functionally different, in that you can perform a lookup on multiple columns with EXISTS, whereas IN only allows for testing one column? (although some people may concatenate columns to work around this limit)

Not disagreeing, just expanding on your answer for those pedants among me. :-P

MM


select geometry::STGeomFromWKB(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  • GilaMonster
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    mister.magoo (6/20/2013)
    Not disagreeing, just expanding on your answer for those pedants among me. :-P


    *sigh*

    Gail Shaw
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    http://sqlinthewild.co.za/index.php/2009/08/17/exists-vs-in/
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