Re: Separate foreign keys with shared ID space

From: Erland Sommarskog <>
Date: Mon, 2 Aug 2004 21:29:26 +0000 (UTC)
Message-ID: <Xns9539EEB1F5AC7Yazorman_at_127.0.0.1>

Daniel Morgan ( writes:
> Erland Sommarskog wrote:

>> Because most real-world look-like keys do not live up to the strict
>> requirements of the primary keys in a database. They are too often
>> nullable or non-unique. Person identification numbers such as SSN 
>> are a good example of both.

> Joe Celko has explained this one to you numerous times and he is
> correct. Little more needs to be said.

Joe Celko has indeed several times explained how SSN are derived, and I assume that he has been talking about SSNs in the US. Whether he is correct on that tidbit is irrelevant, because person identification numbers are formed from other rules elsewhere. Or not formed at all.

But it also true that both you and Celko likes to ride high horse and pretend you know how should model my database, although you don't know my business rules.

So, yes, there is very little more you need to say.

Erland Sommarskog, SQL Server MVP,

Books Online for SQL Server SP3 at
Received on Mon Aug 02 2004 - 23:29:26 CEST

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