Re: PRIMARY KEY on a *group* of columns imply that each column is - Mailing list pgsql-general

On Wed, 2005-04-27 at 02:12, Stephane Bortzmeyer wrote:
> On Tue, Apr 26, 2005 at 03:48:44PM -0500,
>  Scott Marlowe <smarlowe@g2switchworks.com> wrote
>  a message of 26 lines which said:
>
> > Here's a quote from the SQL1992 spec that's VERY clear:
>
> Yes, PostgreSQL is right and implement the standard. Now, what's the
> rationale for the standard? I understand it for a single column but,
> for several columns, it should be still possible to have different
> tuples, such as (3, NULL) and (5, NULL) for instance.

Since NULL <> NULL, that means you could then have

(5,NULL) and (5,NULL) since the two NULLS aren't equal.