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What is the significance of a SELECT statement followed by the number 1 ?

Posted on 2007-04-03
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Last Modified: 2010-03-20
SELECT A.Branch, A.[E-Mail] INTO tblBrEmail From tblBranchEmails A WHERE EXISTS(SELECT 1 from tblFlLNExp  B, tblBranchNotRecd C WHERE Left(B.[CPS Account Number],3)=A.Branch AND Left(B.[CPS Account Number],3)=C.Branch) ORDER BY A.Branch"

What is the significance of the 1 in the (SELECT 1 ...) ?

Can this SQL statement be written without the 1 ?
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Question by:zimmer9
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Raynard7 earned 350 total points
ID: 18847878
the row that is actually returned by the exists statement is irrelevant - exists looks to see if something is returned or not - most databases default to select 1 even if you specify a column - the 1 is faster to produce as it is a constant rather than row data.

so your query is saying where the sub query returns rows then show a.branch .... if it returns no rows then do not show that row from a
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by:sujith80
sujith80 earned 150 total points
ID: 18856759
It needn't be "1". You can select any semantically correct value in the subquery used in EXISTS clause.
Say here, you can change "SELECT 1...." to any of the following, all means the same

SELECT 2 ....
SELECT 'x' ....
SELECT 'hello' ....
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