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Home -> Community -> Usenet -> comp.databases.theory -> Re: One-To-One Relationships

Re: One-To-One Relationships

From: David Cressey <cressey73_at_verizon.net>
Date: Tue, 30 Oct 2007 19:57:39 GMT
Message-ID: <T0MVi.1168$pT.133@trndny07>

"paul c" <toledobythesea_at_ooyah.ac> wrote in message news:0aIVi.160673$1y4.23786_at_pd7urf2no...
> David Cressey wrote:
> > "Phil Reynolds" <philr2354_at_msn.com> wrote in message
> > news:CGzVi.2012$%13.1165_at_newssvr22.news.prodigy.net...
> >> One thing that's not clear to me is when it's appropriate to create a
> >> one-to-one relationship. I mean, in some cases it's obvious, if there's
a
> >> set of data that wouldn't always apply; then you'd want to create that
set
> >> of fields in a separate table with a one-to-one relationship. But in
what
> >> other cases? After the number of fields in a table is greater than X?
> >>
> >> I'm just curious about what thoughts/theories/ideas people have about
> >> one-to-one relationships, because that's something that's never been
> >> entirely clear to me.
> >>
> >
> > I think that a relationship is something you discover, not something you
> > create. Are you talking about creating two tables where there is a
> > one-to-one relationship between rows in table A and rows in table B?
If
> > so, I think what you have created is not the relationship as such, but
a
> > way of representing it in the database.
> >
> > I hope this isn't too nit picky. I think the distinction between what
you
> > discover via analysis and what you create during implementation
(following
> > design) is very fundamental, and needs to be kept clear in all our
> > discussions.
> >
> >
> >

>

> I don't think it's too nit picky at all. I wish the OP had given an
> example because I think people here are talking about two different
> things as you suggest, ie., a one-to-one as the ER people would see it
> (eg., dept has one mgr and mgr has one dept) versus a relation that
> somebody wants to make into two relations.
>

Thanks.

It gets even foggier because many of us (myself included) use the term "relation" in reference to something that, in the strictest mathematical definition, is really a "relationship". Received on Tue Oct 30 2007 - 14:57:39 CDT

Original text of this message

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