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Re: PRIMARY KEY on a *group* of columns imply that each column is NOT - Mailing list pgsql-general

From Tom Lane
Subject Re: PRIMARY KEY on a *group* of columns imply that each column is NOT
Date
Msg-id 21937.1114611990@sss.pgh.pa.us
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In response to Re: PRIMARY KEY on a *group* of columns imply that each column is NOT  (Stephane Bortzmeyer <bortzmeyer@nic.fr>)
Responses Re: PRIMARY KEY on a *group* of columns imply that each column is NOT  (Stephane Bortzmeyer <bortzmeyer@nic.fr>)
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Stephane Bortzmeyer <bortzmeyer@nic.fr> writes:
> Yes, PostgreSQL is right and implement the standard. Now, what's the
> rationale for the standard? I understand it for a single column but,
> for several columns, it should be still possible to have different
> tuples, such as (3, NULL) and (5, NULL) for instance.

If that's what you want, declare it as UNIQUE not PRIMARY KEY.

            regards, tom lane

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