Re: [GENERAL] Fwd: help with uniq index (fwd)

Lorenzo Huerta wrote:
>
> can you all help me with this:
>
> > is there a way to create a unique index on a field
> > (in ver 6.3.1) and also
> > have a single non-uniq value in that value, ie the NULL value?

Why do you ask? Why don't you try first?

vac=> create table t (x int);
CREATE
vac=> create unique index ti on t (x);
CREATE
vac=> insert into t values (1);
INSERT 18444 1
vac=> insert into t values (1);
ERROR: Cannot insert a duplicate key into a unique index
vac=> insert into t values (null);
INSERT 18446 1
vac=> insert into t values (null);
INSERT 18447 1
vac=> insert into t values (null);
INSERT 18448 1

Vadim