Re: Multiple parent design
Date: Sat, 17 Apr 2004 02:19:50 GMT
Message-ID: <av0gc.13656$k05.490_at_newsread2.news.pas.earthlink.net>
Perhaps the design question got lost in the specifics. Let me state the
question in a more generic manner.
Suppose we have entities 1 through N stored in tables Parent1...ParentN.
Now suppose we have a Child entity where each Child instance can be
associated with one and only one Parent instance that may be located in any
one of the tables Parent1 to ParentN.
I'd like to hear any ideas on implementing a design that would prevent the
deletion of a Parent instance if for that instance there existed any Child
instances to which it was associated.
I know of two solutions:
Is there is a more elegent way of solving this problem?
Thomas
"Laconic2" <laconic2_at_comcast.net> wrote in message
news:vu2dnTRAvoIYYuLdRVn-gg_at_comcast.com...
> OK, let's try another approach.
>
> Every in service phone line has a subscriber.
> Every subscriber is either a person or a company.
> Every person that has a phone line is a subscriber.
> Every company that has a phone line is a subscriber.
>
> Can't we start from these assertions, and build the tables from there?
>
>
Received on Sat Apr 17 2004 - 04:19:50 CEST