Re: One-To-One Relationships

On Oct 30, 9:21 am, Gints Plivna <gints.pli..._at_gmail.com> wrote:
> On 30 Okt., 07:53, "Phil Reynolds" <philr2..._at_msn.com> wrote:
>
> > 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.
>
> > Thank you.
>
> I've done it in two cases:
> 1) when I have a feeling (or even promise) that today's requirements
> might change in the future and the 1:1 cardinality might be 1:n after
> a year and
I have done it in this kind of situation as well. As for the rest, it really happens more often (at least, to someone, that, like me, has to pick up crappy DBs quickly produced by someone else who is not a DBA or DB professional in general) to transform the 1:1 into 1 table rather than split 1 table into 2 with 1:1 relationship. Received on Tue Oct 30 2007 - 10:10:07 CET