On 9/6/06, George Pavlov <gpavlov(at)mynewplace(dot)com> wrote:
> I have two columns, both individually nullable, but a row needs to have
> a value in one or the other. What is the best way to implement the
> constraints? I currently have:
>
> create table f (
> a int,
> b int,
> check (a + b is null),
> check (coalesce(a,b) is not null)
> );
>
> Is there a better way to do it?
Personally I woud simply put there
CHECK(a IS NOT NULL OR b IS NOT NULL)
which is probably the simplest form of your constraint. :)