sql-server - Conditional reuse of subquery

Question

Can't figure this out...

Sql stored procedure has an optional argument, say an id(int). For simplicity sake, say, I have to return a result set with extra ...and id=@id check if argument is not null. If not I just return the result set.

How do I avoid writing the 'core' of the query twice? CTE to the rescue?

Answer 1

You could do

where .... and (@id is null or id = @id)

Answer 2

you can try:

select * from myTable where id = isnull(@id, id)

If the @id is null the query compare its own id column to itself, which is always true, otherwise is the parameter used.