Inline
--
Frank
<sanrenkur_at_my-deja.com> schreef in berichtnieuws
8sq3ef$j15$1_at_nnrp1.deja.com...
> In article <39F08952.9BC60BC8_at_home.nl>,
> frank <fbortel_at_home.nl> wrote:
> > In the purest sense, Order No is not a primary identifier. (I reserve
> > the work 'key' for a technical implementation - data modeling does
> > not care about technical implementations).
> > Order No is a result of a technical implementation: the need to be
> > able to identify a particular order fast - computers are fast with
> > numbers, so let's give it a number.
> >
> > The primary (or: unique) identifier is probably a combination of
> > customer name, cust. address, products ordered, date ordered.
>
>
> Order No would be an appropriate primary key if it uniquely identifies
> a table row.
>
Yes, but Order# is "invented" to satisfy computing prerequisites.
>
> > As you can see, you will need a lot of "real world" things to identify
> > a particular order. Better introduce a number - a primary key on a
> table.
>
>
> Why introduce a sequence when you already have an appropriate key.
Like what - order#? How do you think order numbers get generated?
By sequences of some kind. And if not: you're on the wrong track!
>
>
> > BTW: customer would be a better example: people never refer to, or are
> > referred to by numbers, always by name.
>
> What if you have two customers with the same name?
You start getting the picture: see answer to Niall
>
> Sanrenkur
>
>
> Sent via Deja.com http://www.deja.com/
> Before you buy.
Received on Mon Oct 23 2000 - 05:21:37 CDT
