Re: I think my book may be wrong about cardinality, but I'm not sure

From: David Cressey <>
Date: Wed, 25 Jul 2007 12:33:14 GMT
Message-ID: <eqHpi.11862$zy4.2170_at_trndny07>

"JOG" <> wrote in message

> A relationship is a row in a table. Nothing more, nothing less.

I disagree.

Unfortunately, the word "relationship" is used in both E-R modeling and Relational Data modeling. These two usages have a lot of overlap, but they are not exactly the same concept.

A relationship in E-R modeling is NOT a row in a table. It's an association asserted to exist between 2 or more entities, in the real world that the database describes.
The association would exist, even if there were no database in which to record it.

In relational modeling, your comment is correct.

People who see the world exclusively through the lens of the relational data model see all real world relationships as instances of relational data relationships. But that's subjective. Received on Wed Jul 25 2007 - 14:33:14 CEST

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