Re: Constraint Null Value

On Fri, Jun 30, 2006 at 16:41:57 +0200,
  Alex Soto <alex.soto@grifols.com> wrote:
> I am is Alex, and I m developing a product with PostgreSQL 8.1. I have a
> problem. This problem is that i have some unique constraints with
> multi-columns. The problem is that there is some that of the check
> constraint condition that can be null. As it is described in section
> 5.3.3, null of one row is different from the null of other row, so we
> can have two entries with same values inserted because of null value is
> not a considered equal in this comparison.
>
> Is there any administration syntax to change this behavior so null
> values are treated as same value?

No, but you can use partial indexes to impose that constraint. This came
up a couple of months ago on one of the lists and there was a bit more
discussion on the specifics if "use partial indexes" isn't enough of a
hint for you.