Re: Newbie question about db normalization theory: redundant keys OK?

From: Kevin Kirkpatrick <kvnkrkptrck_at_gmail.com>
Date: Tue, 18 Dec 2007 12:35:15 -0800 (PST)
Message-ID: <40957504-43df-453b-8e8e-396f66b2b1e7_at_r29g2000hsg.googlegroups.com>


On Dec 17, 9:57 am, "David Cressey" <cresse..._at_verizon.net> wrote:
> "Bob Badour" <bbad..._at_pei.sympatico.ca> wrote in message
>
> news:47669663$0$5290$9a566e8b_at_news.aliant.net...
>
>
>
>
>
> > David Cressey wrote:
> > > "Dr. Dweeb" <s..._at_dweeb.net> wrote in message
> > >news:476593b3$0$21933$157c6196_at_dreader1.cybercity.dk...
>
> > >>>Would you a) tell the university that the data cannot be modelled and
> > >>>you can't hold it in a database or b) use an artificial key?
>
> > >>This makes my student number 7613861 artifical?
> > >>This makes my employee number 644923 artificial?
>
> > >>One is used by my university, the other by my employer. They may be
> > >>arbitrarily assigned, but they are unique and indicate me alone.
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> > > Artificial in the sense of man made, yes. The assignment of those
> numbers
> > > to you
> > > was purely an arbitrary act, and not based on any naturally observable
> > > charactersitics you have.
>
> > As was your name when (presumably) your parents assigned it to you.
>
> Yes.- Hide quoted text -
>
> - Show quoted text -

When it comes to keys, it comes down to one question: is the underlying attribute meaningful within the universe of discourse? If it is (i.e. the clients know what it means, will use it in conversation, want it in reports, specify it in queries, etc.), it is a natural key and belongs in the database - regardless of whether it is a phonetic name assigned at birth, a social security number assigned upon citizenship, or an id generated and assigned by the database itself. Otherwise, it is garbage (artificial, surrogate, whatever you call it). Received on Tue Dec 18 2007 - 21:35:15 CET

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