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check if variable exists

Author

Topic

KlausEngel
Yak Posting Veteran

85 Posts

Posted - 2012-05-30 : 18:11:46

I have a query that depends on 2 parameters. It's a basic SELECT with a UNION ALL.


select ID, Amount
from table1
where No = @var1
union all 
select ID, Pcs
from table2
where No = @var2

Is it possible to skip the second select statement when @var2 is NULL (or not set)?
Thanks.

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2012-05-30 : 18:17:53

do you mean this?


select ID, Amount
from table1
where No = @var1
union all 
select ID, Pcs
from table2
where No = @var2
AND  @var2 > ''

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

KlausEngel
Yak Posting Veteran

85 Posts

Posted - 2012-05-30 : 18:31:36

I had to modify my query


select ID, Count(ID)
from table1
where No = @var1
group by ID
union all 
select ID, COUNT(ID)
from table2
where No = @var2

This way the second select statement always returns a row even if @var2 is NULL, the count will be '0' but in that case I would rather have the second select statement not be executed. Does that makes sense?

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2012-05-30 : 19:21:00


select ID, Count(ID) AS Cnt
from table1
where No = @var1
group by ID

union all 

select *
from
(
select ID, COUNT(ID) AS Cnt
from table2
where No = @var2
)t
WHERE EXISTS(SELECT 1 WHERE @var2 > '')

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

KlausEngel
Yak Posting Veteran

85 Posts

Posted - 2012-05-31 : 10:48:59

Great - thanks!

visakh16
Very Important crosS Applying yaK Herder

52326 Posts

Posted - 2012-05-31 : 16:07:03

welcome

------------------------------------------------------------------------------------------------------
SQL Server MVP
http://visakhm.blogspot.com/

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