From: Nis Jørgensen <nis@superlativ.dk>
To: pgsql-sql@postgresql.org
Cc: Paul Lambert <paul.lambert@autoledgers.com.au>
Cc: Tom Lane <tgl@sss.pgh.pa.us>
Cc: pgsql-sql <pgsql-sql@postgresql.org>
Subject: Re: Quick question re foreign keys.
Date: Wed, 24 Oct 2007 09:43:10 +0200
Message-ID: <471EF78E.8050503@superlativ.dk> (raw)
In-Reply-To: <20071024012705.5f253946.darcy@druid.net>
References: <471EA7D5.9040403@autoledgers.com.au>
<21715.1193193880@sss.pgh.pa.us>
<471EB55F.5050600@autoledgers.com.au>
<20071024012705.5f253946.darcy@druid.net>
D'Arcy J.M. Cain skrev:
> On Wed, 24 Oct 2007 11:00:47 +0800
> Paul Lambert <paul.lambert@autoledgers.com.au> wrote:
>> It's marked not null as a result of being part of the primary key for
>> that table which I can't really get around.
>>
>> I can get away with not having the foreign key though, so I'll have to
>> go down that path.
>
> It can't be the primary key and have NULLs. It sounds to me like you
> have a design problem somewhere.
Well, I have a couple of times had the "need" to have a primary
key/uniqueness constraint with one column nullable (indicating "Not
Applicable"). The "problem" is that we have only one NULL, which for
comparison purposes is interpreted as "Not Known".
Nis
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To: pgsql-sql@postgresql.org
Cc: nis@superlativ.dk, paul.lambert@autoledgers.com.au, tgl@sss.pgh.pa.us
Subject: Re: Quick question re foreign keys.
In-Reply-To: <471EF78E.8050503@superlativ.dk>
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