Subject: Re: surrogate key or not?
From: Markus Bertheau <twanger@bluetwanger.de>
To: sad <sad@bankir.ru>
Cc: pgsql-sql@postgresql.org
In-Reply-To: <200407211144.01001.sad@bankir.ru>
References: <1090325769.3241.27.camel@dicaprio.akademie1.de>
	<004101c46ec2$631ca930$7201a8c0@mst1x5r347kymb>
	<200407210001.00102.josh@agliodbs.com>
	<200407211144.01001.sad@bankir.ru>
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Message-Id: <1090407515.3239.4.camel@dicaprio.akademie1.de>
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Date: Wed, 21 Jul 2004 12:58:35 +0200
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=D0=92 =D0=A1=D1=80=D0=B4, 21.07.2004, =D0=B2 09:44, sad =D0=BF=D0=B8=D1=88=
=D0=B5=D1=82:

> 4) Replication:  to identify an object of ANY type (record of any table=
=20
> regardless to datamodel), to store lists of deleted or modified objects=
=20
> (regardless to datamodel)

That sounds like a datamodel on data that belongs to another data model,
and 5) applies.

> 5) Making a primary key: if there is no real key at all.

When there's no key at all, there can't be a surrogate key, as I
understand it. In such cases a generated unique number comes in handy,
and it's a real primary key and no surrogate key.

=D0=A1=D0=BF=D0=B0=D1=81=D0=B8=D0=B1=D0=BE

--=20
Markus Bertheau <twanger@bluetwanger.de>