Re: One-to-many with a twist

Thanks!

I don't want to go the many-to-many route, as I want to maintain "delete-on-removal" logic (I'm using Hibernate for my persistence layer, and it will not delete unreferenced items from n-to-m, only 1-to-n)

DA Morgan wrote:
> martind-crap1_at_mailblocks.com wrote:
> > Hi,
> >
> > What is the best way to model this: Assume I have two objects: Agency
> > and Publisher, and both have a 1-to-n relationship to Employee. This is
> > a true 1-to-n relationship, as each Employee can only work for one
> > Agency or one Publisher. Let's assume further that I cannot introduce a
> > supertype (e.g. Employer) which holds the 1-to-n relationship.
> >
> > My preferrd solution is to have a foreign key in Emplyee that can
> > either link to a primary key of Agency or Publisher (all my primary
> > keys are 64-bit IDs that are unqiue across the database). However, now
> > I won't be able to map a bi-directional association, without indicating
> > in Employee whether this is an "Agency" or "Publisher" relationship
> > (ala <ANY>).
> >
> > My other option is to use two tables, AgencyEmployee and
> > PublisherEmployee, which can then be linked as traditional 1-to-n
> > bidirectional associations.
> >
> > What do you guys consider best practice in this situation?
> >
> > Cheers,
> >
> > Jen
>
> Over a period of time an employee can be both even if at any specific
> point-in-time only 1. I would model it as a many-to-many with an
> intersecting entity and a unique constraint to make it impossible for
> someone to simultaneously be both if such is the case.
>
> --
> Daniel A. Morgan
> http://www.psoug.org
> damorgan_at_x.washington.edu
> (replace x with u to respond)
Received on Mon May 30 2005 - 14:07:12 CDT