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UNION with IF clause

Author

Topic

Ciupaz
Posting Yak Master

232 Posts

Posted - 2012-12-05 : 08:08:18

Hello all,
in a my stored procedure, I have several SELECT combined to an UNION to get my results.
Something like this:

Select Field1,Field2
From TableA A inner join TableB B
On A.ID = B.ID

UNION

Select Field1,Field2
From TableC C inner join TableD D
On C.ID = D.ID

UNION

Select Field1,Field2
From TableE E inner join TableF F
On E.ID = F.ID

Then I have to add another Select block only if a condition is valid, like:

IF (@DataDaUTC<= @DataStartNBDO)

Select Field1,Field2
From TableY Y inner join TableZ Z
On Y.ID = Z.ID

but in this way does not work in SQL Server 2008.

How can I solve this problem?

Thanks in advance.

Luigi

sunitabeck
Master Smack Fu Yak Hacker

5155 Posts

Posted - 2012-12-05 : 08:11:48

Instead of using the if clause, insert your condition as a where clause


....
UNION 

Select Field1,Field2
From TableE E inner join TableF F
On E.ID = F.ID

UNION

Select Field1,Field2
From TableY Y inner join TableZ Z
On Y.ID = Z.ID
WHERE @DataDaUTC<= @DataStartNBDO

jimf
Master Smack Fu Yak Hacker

2875 Posts

Posted - 2012-12-05 : 08:14:21

Those params aren't part of the table, so brute force may work

IF @DataDaUTC <= @DataStartNBDO
Select Field1,Field2
From TableA A inner join TableB B
On A.ID = B.ID

UNION

Select Field1,Field2
From TableC C inner join TableD D
On C.ID = D.ID

UNION

Select Field1,Field2
From TableE E inner join TableF F
On E.ID = F.ID

UNION

Select Field1,Field2
From TableY Y inner join TableZ Z
On Y.ID = Z.ID

ELSE

Select Field1,Field2
From TableA A inner join TableB B
On A.ID = B.ID

UNION

Select Field1,Field2
From TableC C inner join TableD D
On C.ID = D.ID

Jim

Everyday I learn something that somebody else already knew

Ciupaz
Posting Yak Master

232 Posts

Posted - 2012-12-05 : 08:28:04

Thank you Sunita and Jim
I've adopted the Sunita's solution.

Luigi

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