Re: Setting unique constraints.

> -----Original Message-----
> From: Anil Jangam [mailto:anilj@indts.com]
> Sent: 18 December 2001 06:13
> To: 'Dave Page'; pgsql-cygwin@postgresql.org
> Subject: Setting unique constraints.
> Importance: High
>
>
> Hi,
>
> Is there any way to apply the unique constraint on the
> attribute of a table through the pgAdmin?. This certainly
> other than applying the primary key constraint on the attribute.

Yes, assuming your data is already unique, you can just create a unique
index on the column(s) required. This is how PostgreSQL enforces unique
constraints when you added them with CREATE TABLE.

> To set the foreign key relationship it is the basic
> requirement that the referenced attribute should be a primary
> key in the referenced table.

I'm not sure this is the case.

> Can I achieve FK relationship without making it a primary
> key?? Because I have already defined a PK, which does not
> contain the referenced attribute. If it is possible to have a
> unique attribute rather having PK and then achieve the FK.

I don't think you need to define a primary key or unique constraint. Just
add the foreign key when you define the table - if PostgreSQL doesn't like
it it will certainly tell you about it.

Regards Dave.