use CASE without ELSE in WHERE clause like IF

Question

Is it possible to use a CASE without ELSE in WHERE clause like an IF? for put a condition or not.

Example

WHERE monto = 100
    AND CASE WHEN @canal is not null
        THEN canal = @canal
    END

I ask this because I want to do this

WHERE monto = 100
    IF (@canal is not null){
        AND canal = @canal
    }

Answer 1

You need to include this condition in the WHERE:

WHERE monto = 100 AND ( @canal IS NULL OR canal = @canal )

If it's actually in a stored-procedure it might be more efficient if you use an IF...ELSE around the different queries, one with this parameter and one without.