Re: Objects and Relations

From: Roy Hann <specially_at_processed.almost.meat>
Date: Wed, 14 Feb 2007 16:22:24 -0000
Message-ID: <>

"Marshall" <> wrote in message
> On Feb 14, 7:14 am, "Roy Hann" <specia..._at_processed.almost.meat>
> wrote:
>> >> As an addendum, once implemented a surrogate key becomes a natural
>> >> key. I find this fascinating - it seems somehow analagous to "Nature
>> >> abhoring a vacuum".
>> > I think it has more to do with the human drive to communicate.
>> I struggle with that. If, for some reason, I choose to say (just) that,
>> "I
>> have a tin of cat food, and its name shall be 1345235", what have I
>> communicated? No one in the real world could ever point it out and say,
>> "Hey! There goes 1345235." And nor could I.
> Let's think of customers and customer ids; it's a very similar case.

Actually no. I deliberately wrote: 'I choose to say (just) that, "I have a tin of cat food, and its name shall be 1345235"', with emphasis on "just". Any attempt to distinguish individual cans is probably spurious. Yet people do often try to do such things in databases. (Wrongly IMO.)

> What does this communicate? It communicates customer
> identity.

No question, although in the real world it communicates only through familiarity over time, and only because customers are not in every way interchangeable.

The point I am groping towards (I think) is that surrogates are exactly that. They stand in place of something else you could have used albeit perhaps less conveniently. But if there is nothing else, what does the surrogate stand in place of?

Roy Received on Wed Feb 14 2007 - 17:22:24 CET

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