On Wed, May 28, 2003 at 15:34:41 +0200,
Mauro Bertoli <bertolima@yahoo.it> wrote:
> INSERT INTO questiontypes (id,flags,label) values
> (2,null,'a');
>
> and re-insert it... I can!!!! Now there are two
> identical row, and UNIQUE??
> I think postgres must occur an error? Is it Ok?
This is how unique constraints work. Any null value is considered as
different from any other null value. If that isn't how you want things
to work, using some value other than null to represent whatever you
are using null to represent.