Re: Database design, Keys and some other things

From: David Cressey <david.cressey_at_earthlink.net>
Date: Sat, 01 Oct 2005 13:38:54 GMT
Message-ID: <Ojw%e.7060$QE1.1582@newsread2.news.atl.earthlink.net>

"mAsterdam" <mAsterdam_at_vrijdag.org> wrote in message news:433cf1d0$0$11072$e4fe514c_at_news.xs4all.nl...

> There is an important difference. Unless we are talking about
> that specific "*some*" database, the VIN is /not/ a surrogate key in
> the database at hand.

Agreed. This is an important difference.

Perhaps the difference is between "externally supplied data" and "internally generated data". In a typical personnel system, new employee ids are assigned by the HR department, and they are responsible, ultimately, for avoiding duplicate assignments. The IT department ultimately is only a custodian of data that the HR department "owns". Of course, the IT department codes duplicate rejection somewhere into their systems, so as to help HR discover their errors in a timely fashion.

So, when we have a "surrogate key in the database at hand" (or, if you can accept it, "in the system at hand") what we have is data that is "owned" by the system itself, rather than merely kept in custody by the system for its owners. Received on Sat Oct 01 2005 - 08:38:54 CDT