Question

I have a stored procedure that needs to return something from one of two databases:

IF @x = 1
    SELECT y FROM Table_A
ELSE IF @x = 2
    SELECT y FROM Table_B

Either SELECT alone will return what I want, but adding the IF/ELSE makes it stop returning anything. I tried:

IF @x = 1
    RETURN SELECT y FROM Table_A
ELSE IF @x = 2
    RETURN SELECT y FROM Table_B

But that causes a syntax error.

The two options I see are both horrible:

1. Do a UNION and make sure that only one side has any results:

   SELECT y FROM Table_A WHERE @x = 1
   UNION
   SELECT y FROM Table_B WHERE @x = 2

2. Create a temporary table to store one row in, and create and delete it every time I run this procedure (lots).

Neither solution is elegant, and I assume they would both be horrible for performance (unless MS SQL is smart enough not to search the tables when the WHERE class is always false).

Is there anything else I can do? Is option 1 not as bad as I think?

Answer 1

are you sure that @x is 1 or 2?

declare @x int

set @x = 1

IF @x = 1
    SELECT 'syscolumns',* FROM syscolumns
ELSE IF @x = 2
    SELECT 'sysobjects',* from sysobjects
    else
    select 'not 1 or 2'

BTW what is this line supposed to do

SELECT @y FROM Table_B

it will just return the same variable @y for however many rows you have in TableB

based on you comment, 0 means success, the proc did not error out. Don’t use a return statement, use an output parameter instead

based on your second comment you can use this, note this will only work in a proc since inline sql cannot use the return statement

declare @y int,@x int
select @y = -500


IF @x = 1
    SELECT  @y = y FROM Table_A
ELSE IF @x = 2
    SELECT  @y = y FROM Table_B

return @y