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Re: Has E/R had a negative impact on db?

From: -CELKO- <jcelko212_at_earthlink.net>
Date: 23 Apr 2006 19:55:33 -0700
Message-ID: <1145847333.011707.268340@z34g2000cwc.googlegroups.com>


>> Huh? An entity in E/R corresponds to a relation in an RDBMS. A relationship in E/R corresponds to a relation in an RDBMS. <<

One problem is that a relationship in a ER diagram is a line between boxes. That puts us in a binary-only world. ORM, on the other hand, allows n-ary relationships. And the diagram has no other information about the nature of the relationship, like ORM does.

The map becomes the territory. And when you look at query generating tools based on ER diagrams, they tend "follow the lines", so to answer a questlon like "Who was in the mail room the day we invoiced XYZ company?" becomes a chain of joins instead of a match on two date columns. Received on Sun Apr 23 2006 - 21:55:33 CDT

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