Re: constraint -- one or the other column not null - Mailing list pgsql-general

On 9/6/06, George Pavlov <gpavlov@mynewplace.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. :)