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What is mean by 0 = 1 In Where statement in DB2

 
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callkris_cit

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Joined: 22 Apr 2006
Posts: 44

PostPosted: Thu Feb 22, 2007 4:01 pm    Post subject: What is mean by 0 = 1 In Where statement in DB2
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Hi All,

Select * from tablename where 0 = 1. What does it mean?

Regards
Suresh
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guptae

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Joined: 14 Oct 2005
Posts: 1187
Location: Bangalore,India

PostPosted: Thu Feb 22, 2007 4:04 pm    Post subject:
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Hi Suresh,

It would not fetch any row since 0 never be equal to 1
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silan

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Joined: 16 Jun 2006
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Location: new delhi

PostPosted: Thu Feb 22, 2007 4:43 pm    Post subject: Re: What is mean by 0 = 1 In Where statement in DB2
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Hi,

This is a very common technique used for tuning.

0 = 1 predicate is used to influence the access path .

Ex:SELECT CORP_CODE,SALES_OFFICE
FROM TABLE1
WHERE CORP_CODE IN ('10' , '20') OR '0=1';;;;

u can get more on this from Mullins book.

-cheers.
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