From: Leif B. Kristensen <leif@solumslekt.org>
To: pgsql-sql@postgresql.org
Subject: Re: Need help with 'unique parents' constraint
Date: Mon, 12 Sep 2005 20:02:34 +0200
Message-ID: <200509122002.34864.leif@solumslekt.org> (raw)
In-Reply-To: <7a5b3f3e2ddebaeda6d9df07ebca943a@biglumber.com>
References: <7a5b3f3e2ddebaeda6d9df07ebca943a@biglumber.com>
On Sunday 11 September 2005 16:04, Greg Sabino Mullane wrote:
> Not just old-fashioned, it's the biological law! (among homo sapiens
> anyway). I'd approach this with a trigger, as you can do complex
> checks and get back nice customized error messages. A sample script
> follows. Hard to tell without seeing your whole schema, but I see no
> need for a relation_id primary key if you already have a unique
> constraint on child_fk and parent_fk, so I made those into the
> primary key for the relations table:
Thank you for an excellent answer. I think I will have to study your
code for a while. But is it such a bad idea to have a separate column
for the primary key here? I see that there are two schools on this,
with diametrically opposed views. For my own part, I feel that it at
least doesn't hurt to have a surrogate key. Secondly, a single key
value is easier to reference from another table than a composite key.
--
Leif Biberg Kristensen
http://solumslekt.org/
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To: pgsql-sql@postgresql.org
Cc: leif@solumslekt.org
Subject: Re: Need help with 'unique parents' constraint
In-Reply-To: <200509122002.34864.leif@solumslekt.org>
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