Re: candidate keys in abstract parent relations

Forrest L Norvell wrote:
> ...
> Also, on a more abstract level, I'm trying to derive a method for
> dealing with similar problems in the future. It seems to me like this
> is a common problem when trying to model real-world domains,...

Right, I think. Very common for "keys" to be re-used. That's why the biggest Canuck 'phone company used to send two bills if a customer had two phones and airline systems are complicated because IATA allows a flight number to be re-used the next day and cash registers re-use transaction numbers if the power cord is pulled.

The original post mentioned candidate keys which seems to me to be the important ingredient. I can't see anything wrong with having two of them in the same relation, eg., {Number} and {Title, Label, ReleaseDate}, ie., they are 'one-to-one'. Use {Number} in the other tables. If you ever discover that the other candidate key is insufficient, you can 'extend' it with a single table change. Depending on what users want to know, you might not even have to change any queries.

(I forget who said you can solve any problem with enough indirection but it seems to apply here).

p Received on Thu Jan 19 2006 - 11:14:55 CST