Re: Composite Unique Key - Doubt

On Jun 20, 2013, at 1:56 AM, Technical Doubts <online.technicaldoubts@gmail.com> wrote:

> Am using Postgres 9.2
>
> I am having a table
>
> technologies
> (
> technologyid bigint,
> status character(1),
> implementeddate date
> *CONSTRAINT technologies_uq UNIQUE (technologyid, status, implementeddate)*
> )
>
> entering data as
>
> insert into technologies (technologyid,status,implementeddate)
> values
> (123,'P',null),
> (123,'P',null);
>
> 2 rows affected.
>
> table accepting duplicate values in spite of composite unique constraint..
> where I am doing wrong?

Reason is null is not equal to null.

So, 123,'P',null and 124,'P',null is actually unique composite key.

Thanks & Regards,
Vibhor Kumar
EnterpriseDB Corporation
The Postgres Database Company
Blog:http://vibhork.blogspot.com