(PersonID, PhoneID) represents a many-to-many relationship between persons
and phones.
As long as we are going to talk about "entities", we might as well talk
about "relationships" as well.
When you get down to designing your relations, it's sort of a moot point,
because you will use relations to hold data about entities, data about weak
entites, and data about relationships.
The advantages of using Entity-Relationship (ER or ERD) modeling to think
about the problem, is that it allows you to distinguish between ANALYSIS
and DESIGN. Your ER model captures what you think you know about persons
and phones. That's analysis.
Your relational model pertains to the solution, not the problem. That's
design.
Design issues and analysis issues have been smashed together in this
discussion. You can do that if you want, but I recommend keeping them
separate.
Received on Sun Oct 17 2004 - 13:30:21 CEST