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Re: PRIMARY KEY on a *group* of columns imply that each column is NOT

From: Stephane Bortzmeyer <bortzmeyer(at)nic(dot)fr>
To: Scott Marlowe <smarlowe(at)g2switchworks(dot)com>
Cc: Stephane Bortzmeyer <bortzmeyer(at)nic(dot)fr>,Patrick TJ McPhee <ptjm(at)interlog(dot)com>, pgsql-general(at)postgresql(dot)org
Subject: Re: PRIMARY KEY on a *group* of columns imply that each column is NOT
Date: 2005-04-27 15:00:17
Message-ID: 20050427150017.GB2740@nic.fr (view raw or flat)
Thread:
Lists: pgsql-general
On Wed, Apr 27, 2005 at 09:36:57AM -0500,
 Scott Marlowe <smarlowe(at)g2switchworks(dot)com> wrote 
 a message of 18 lines which said:

> Often the best bet here, btw, is to declare it not null then use
> something other than null to represent null, like the text
> characters NA or something.

Yes, but it defeats the purpose of NULL. And what should I use as a
"pseudo-NULL" value for INET? 127.0.0.1? 0.0.0.0? Special values are
well-known for the problems they raise. That's why many languages have
NULL-like solutions (None in Python, undef in Perl, Maybe types in
Haskell, etc).


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Subject: Re: PRIMARY KEY on a *group* of columns imply that each
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