Re: One-To-One Relationships

From: paul c <>
Date: Tue, 30 Oct 2007 15:34:20 GMT
Message-ID: <0aIVi.160673$1y4.23786_at_pd7urf2no>

David Cressey wrote:
> "Phil Reynolds" <> wrote in message
> news:CGzVi.2012$

>> 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. Received on Tue Oct 30 2007 - 16:34:20 CET

Original text of this message