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short circuiting dynamic sql queries

Posted on 2008-11-17
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Last Modified: 2012-05-05
Hi,

I'm in a bit of a jiffy here...

I'm trying to short-cicuit a sql query here, where if the value in the where clause is null then it'll query all records else, query only the values in the where clause.

here's my code...

declare @filter as varchar(50)
declare @SQLCmd as varchar(4000)

set @filter = 'xxxx' -
set @SQLCmd =  'select * from table
      where  NOT ('+@filter+' IS NOT NULL and table.field <> '+@filter+' )'
exec (@SQLCmd)      
      

this code works when @filter contains values on every executing. my problem is when i try to execute the code where @filter = null, @SQLCmd is null all in all..
ideally, the query should look like this:

select * from table
      where  NOT (null IS NOT NULL and table.field <> null )
 
can someone provide me with some tips?
subsequently, how do i make this work using a where... in clause?

thanks
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Question by:praetorean
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3 Comments
 
LVL 75

Expert Comment

by:Aneesh Retnakaran
ID: 22974073
You dont really need dynamic sql here

declare @filter as varchar(50)
set @filter = 'xxxx' -
select * from table
where (@Filter IS NULL or  field like '%'+@Filter+'%' )

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Accepted Solution

by:
praetorean earned 0 total points
ID: 22994158
i got it already... what i did was validate the value of the parameter... if = null then, i bypass and not add an additional where clause. if <> null, then i add an additional where clause...
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LVL 75

Expert Comment

by:Aneesh Retnakaran
ID: 22994349
if there is only one filter then this will be better

IF @Filter is Null
     select * from table
ELSE
     select * from table where ield like '%'+@Filter+'%'
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