Re: PRIMARY KEY on a *group* of columns imply that each column is NOT

On Wed, Apr 27, 2005 at 05:04:07PM +0200,
Sebastian Böck <sebastianboeck(at)freenet(dot)de> wrote
a message of 24 lines which said:

One is enough :-)
vvvvv
> 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;

Great! It works fine. Many thanks.

tests=> select * from x;
name | address
------+---------
foo |
foo | 1.2.3.4
foo | ::1
bar | ::1
bar |
(5 rows)
tests=> insert into x (name) values ('bar');
ERROR: duplicate key violates unique constraint "n"
tests=> insert into x (name, address) values ('bar', '::1');
ERROR: duplicate key violates unique constraint "na"
tests=> insert into x (name) values ('new');
INSERT 21128 1