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BOOK: Beginning Database Design Solutions ISBN: 978-0-470-38549-4
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Old March 15th, 2012, 02:07 PM
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Default Figure 5-29 page 116

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.
Old March 15th, 2012, 03:55 PM
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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 Stephens, Microsoft MVP

Essential Algorithms: A Practical Approach to Computer Algorithms

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