>Hi
>
>How would I modify this SQL statement so that if a MessageID exists in both tables, the resulting table should ONLY take the record from the ApplicationMessage table?
>
>select * from dbo.SystemMessage where MessageID = @LnMessageID
> union all
>select * from dbo.ApplicationMessage where MessageID = @lnMessageID
>order by MessageID
>
>Regards

The simplest way would be

select * from dbo.SystemMessage where MessageID = @LnMessageID
and not exists (select 1 from dbo.ApplicationMessage where MessageID = @lnMessageID)
   union all 
select * from dbo.ApplicationMessage where MessageID = @lnMessageID
order by MessageID