sql question, alternative to if-else for this example?

Question

Hi Guys,

DECLARE @cityID bigint;
set @cityID = NULL
--set @cityID = 3

SELECT ID,
        Name,
        CityID,
        IsProvince
FROM TABLE t
    WHERE ISNULL(t.CityID, -1) = ISNULL(@cityID, -1)

whenever the @cityID is NULL the t.CityID is also NULL for that record.

Only one record can ever be true for IsProvince

Is there a way to check without doing the if-else clause if I want to do the following:

1) If the @cityID is NULL, then get the record whose IsProvince is 1

2) If the @cityID is NOT NULL then get the record whose CityID = @cityID

Thanks,

Voodoo

Answer 1

You can do this in the WHERE:

DECLARE @cityID bigint;
set @cityID = NULL
--set @cityID = 3

SELECT ID,
        Name,
        CityID,
        IsProvince
FROM TABLE t
    WHERE (@cityID IS NULL AND t.CityID IS NULL AND IsProvince = 1)
          OR (t.CityID = @cityID)

This should work since anything = NULL always returns false. The first clause should solve your #1, and the second solves #2. I'm not sure if you really need the t.CityID IS NULL clause though, since your criteria for #1 doesn't mention it.

Does this make sense?