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Date: Tue, 23 Jun 2009 12:44:12 -0600
From: Joshua Tolley <eggyknap@gmail.com>
To: Harald Fuchs <hari.fuchs@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Composite primary keys
Message-ID: <20090623184412.GG27474@eddie>
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On Tue, Jun 23, 2009 at 05:14:36PM +0200, Harald Fuchs wrote:
>   test=# CREATE TABLE t2 (
>   test(#   id int NOT NULL REFERENCES t1,
>   test(#   language char(3) NULL,
>   test(#   txt text NOT NULL,
>   test(#   PRIMARY KEY (id, language)
>   test(# );
>   CREATE TABLE

<snip>

>   test=# INSERT INTO t2 (id, language, txt) VALUES (2, NULL, 'text 1 no language');
>   ERROR:  null value in column "language" violates not-null constraint

Primary keys are NOT NULL and UNIQUE. You can't have null values in a primary
key.

- Josh / eggyknap

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