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

Stephane Bortzmeyer wrote:
> On Wed, Apr 27, 2005 at 04:50:23PM +0200,
>  Sebastian Böck <sebastianboeck@freenet.de> wrote
>  a message of 48 lines which said:
>
>
>>CREATE UNIQUE INDEX na ON x (name, address) WHERE address IS NULL;
>
>
> No, because it prevents two tuples with the same value of "name".

Ahh, sorry! Ment something more like:

CREATE TABLE table x (
   name TEXT NOT NULL,
   address INET
);

CREATE UNIQUE INDEX na ON x (name, address);
CREATE UNIQUE INDEX n ON x (name) WHERE address IS NULL;

HTH

Sebastian