Re: null as part of key?

i agree that a non business id would work.

i don't understand why null is not a valid value for a key part but is ok for a unquie index.

"Henning Follmann" <h.follmann_at_gmx.de> wrote in message news:slrn9tamm8.hl.h.follmann_at_mobile.follmann-net...
> On Mon, 22 Oct 2001 11:40:57 -0400, ed zappulla <zappullae_at_rcn.com> wrote:
> > I see. What about this case
> >
> > country
> > state
> > city
> > some other cols
> >
> > pk = country, state, city
> >
> > Some contries don't have states; therefore it would be null for those
> > countries.
> >
>
> The problems you are just encountering show some flaws in your
> datamodeling.
>
> 1) do not use production data as a primary key
>
> This is a good rule!
>
> Suggestion:
>
> Create a metadata table:
> it includes for every country the meta information about address formats.
> Use for the countries the iso standard! Sooner or later you will be
> thankfull you did so!
>
> now the rough design
>
> Party : Party_ID, PartyType_ID
>
> Address: Party_ID, AddressMeta_ID, ...
>
> AddressMeta: AddressMeta_ID, Country_ID, Field1, Field1Flag (Mand, Opt,
> notuse) ...
>
> Country: Country_ID (Num(3)), Name, A2, A3
>
>
>
>
> I use also Party, because you might have Companies, private Persons ...
> A Party might have also more than one Address, so you might tweak it for
> your purposes.
> It might also a good idea to place some rules for checking the data
> depending on the country. If you use MetaData this gives you the
> flexibility to stor the validation rules (names of procedures) in your
> table.
>
>
> Good luck,
> dealing with international addresses, currencies, etc. is not easy.
> I hope this helps.
>
>
>
>
> > does this make sense?
> >
> >
> >
> > "Niall Litchfield" <n-litchfield_at_audit-commission.gov.uk> wrote in
message
> > news:3bd42f49$0$237$ed9e5944_at_reading.news.pipex.net...
> >> No. Nor in any version. If you think carefully you will see that
allowing
> >> this would be a nonsense.
> >>
> >>
> Cheers,
> henning
>
> --
> Henning Follmann | 8 Jane Road
> Tel.: +1 908 656 7061 | New Providence, NJ 07974
> H.Follmann_at_gmx.de | USA
>
>
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Received on Tue Oct 23 2001 - 10:37:58 CDT