Hello all,

I have a question regarding the cardinality in the ER Diagram in figure 5-29 on page 116:

How come Order has a 1.N cardinality with Customer while Address and Contact have a 0.N cardinality?

The Customer needs at least one order, one address, and one contact, so shouldn't the cardinality be the same in all 3 relationships?

Thanks in advance for any help.

Hi Meer,

I think that must be a mistake. I could imagine allowing a Contact or Address to exist without a corresponding Customer but I don't think that fits the model described here.

So I think they should all be labeled 1.N.

__________________
Rod

Rod Stephens, Microsoft MVP

Essential Algorithms: A Practical Approach to Computer Algorithms

(Please post reviews at Amazon or wherever you shop!)