>Hi
>
>I'm performing the following stored procedure to essentially join 2 tables, with identical structures, to amalgamate the list of system/application messages into one dataset:
>
>as
>begin
>set nocount on;
>select * from dbo.SystemMessage union all select * from dbo.ApplicationMessage order by MessageID
>end
>
>I now want to pass a parameter into this stored procedure, @lnMessageID, and I'd like the statement to perform the join and THEN return the record from the joined results that matches @lnMessageID. @lnMessageID is always unique.
>
>Regards

In my opinion, it would be easier to add WHERE condition to both parts instead, e.g.

select * from dbo.SystemMessage where MessageID = @LnMessageID
   union all 
select * from dbo.ApplicationMessage where MessageID = @lnMessageID
order by MessageID 

Alternatively, you can go with the derived table, but I don't see a benefit.