From: Tom Lane <tgl@sss.pgh.pa.us>
To: Joshua Tolley <eggyknap@gmail.com>
Cc: Harald Fuchs <hari.fuchs@gmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Composite primary keys
Date: Tue, 23 Jun 2009 15:15:17 -0400
Message-ID: <24680.1245784517@sss.pgh.pa.us> (raw)
In-Reply-To: <20090623184412.GG27474@eddie>
References: <pu1vpb2d9f.fsf@srv.protecting.net>
<20090623184412.GG27474@eddie>
Joshua Tolley <eggyknap@gmail.com> writes:
> Primary keys are NOT NULL and UNIQUE. You can't have null values in a primary
> key.
On reflection I think the OP's beef is that we complain about this:
regression=# create table t (f1 int null not null);
ERROR: conflicting NULL/NOT NULL declarations for column "f1" of table "t"
but not this:
regression=# create table t (f1 int null primary key);
NOTICE: CREATE TABLE / PRIMARY KEY will create implicit index "t_pkey" for table "t"
CREATE TABLE
even though the implied NOT NULL is really a conflict. I think we could
fix that case if we cared to. However, since the NULL clause is
forgotten about after parsing, there isn't anything we could do to raise
a complaint about doing it in two steps:
regression=# create table t (f1 int null);
CREATE TABLE
regression=# alter table t add primary key(f1);
NOTICE: ALTER TABLE / ADD PRIMARY KEY will create implicit index "t_pkey" for table "t"
ALTER TABLE
(barring remembering the NULL clause in the catalogs, which seems
entirely silly). So I'm not sure how interesting it is to complain
about the single-command case.
regards, tom lane
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To: pgsql-sql@postgresql.org
Cc: tgl@sss.pgh.pa.us, eggyknap@gmail.com, hari.fuchs@gmail.com
Subject: Re: Composite primary keys
In-Reply-To: <24680.1245784517@sss.pgh.pa.us>
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