PostgreSQL Discussion - Re: PRIMARY KEY on a *group* of columns imply that each

You are viewing an archived Text-only version of the thread. To view this thread in it's original format and/or if you want to reply to this thread please [click here]

Author

Re: PRIMARY KEY on a *group* of columns imply that each

Stephan Szabo

2005-04-27, 9:23 am

On Wed, 27 Apr 2005, Stephane Bortzmeyer wrote:

> On Tue, Apr 26, 2005 at 03:48:44PM -0500,
> Scott Marlowe < smarlowe@g2switchwor
ks.com> wrote
> a message of 26 lines which said:
>
>
> 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.

The case that they're trying to prevent is two tuples like (3, NULL) and
(3,NULL) since uniqueness alone doesn't prevent them both from being
inserted.

---------------------------(end of broadcast)---------------------------
TIP 2: you can get off all lists at once with the unregister command
(send "unregister YourEmailAddressHere
" to majordomo@postgresql
.org)

Sponsored Links