On Wed, Jan 25, 2006 at 08:39:00AM -0800, MargaretGillon@xxxxxxxxxxxxxx wrote: > I have taken your suggestion and changed the values to NULL for the empty > foreign keys. Thank you for the constraint. I modified it to check for > NULL and it works great. > > ALTER TABLE event > ADD CONSTRAINT two_nulls_1 CHECK (((((evenid1 IS NULL) AND (evevid1 IS > NULL)) OR ((evevid1 IS NULL) AND (evreid1 IS NULL))) OR ((evenid1 IS NULL) > AND (evreid1 IS NULL)))); Is there a requirement that exactly one column be NOT NULL? If so then you'll need to add a check for that because this constraint would allow all three to be NULL. -- Michael Fuhr
