Обсуждение: Constraint Null Value

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?

Thank you very much.


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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.