Re: Create a foreign key from a field that is part of a mulitple primary key

Daniel Morgan <damorgan_at_x.washington.edu> wrote in message news:<1094424340.174831_at_yasure>...
> Niall Litchfield wrote:
> > "Mark C. Stock" <mcstockX_at_Xenquery .com> wrote in message
> > news:SbSdnR0ccbBME6rcRVn-sQ_at_comcast.com...
> >
> >>so, if you're offended, sorry. but if you're up for a lively discussion,
> >
> > why
> >
> >>not post a structure that you feel requires more than one column for the
> >>PK -- either we'll see each other's side better, or you'll have the
> >>satisfaction of proving me wrong ;-)
> >
> >
> > A possibility for you. We have an helpdesk app. It contains, not entirely
> > surprisingly, an inventory table. That table contains the fields MODEL and
> > SERIAL#, we use (MODEL,SERIAL#) as the PK. I'm not prepared to guarantee
> > uniqueness of the serial# across manufacturers and over time. I am prepared
> > to gurantee the uniqueness of SERIAL# across the same model from the same
> > manufacturer over time. I'll grant you that we could use an artificial key
> > (and in fact it would be my preference), never the less for the design of
> > the app the important thing is that it is an item of inventory (not that it
> > is a laptop made by manufacturer y or a router made by company Z).
>
> You do understand, I presume, that if it was done your way you could
> easily get duplicate model, serial#s into your table or be forced to
> create a unique constraint (with its index) do duplicate exactly what
> it is that your PK does for you now.

Daniel, are you replying to me or Mark here? If me I don't quite understand your point.

Niall Litchfield
Oracle DBA
http://www.niall.litchfield.dial.pipex.com Received on Wed Sep 08 2004 - 05:40:02 CDT