Re: Contact DB, relational design, opinions please

From: David Cressey <>
Date: Wed, 05 Sep 2001 14:44:44 GMT
Message-ID: <wTql7.429$>

Learn how to express the requirements in the form of an ER (Entity Relationship) model.

Learn how to normalize.

Learn when to normalize.

Learn what to do when you don't normalize.

Study some good designs.

NULLS can help you if you use them right. They can shoot you in the foot if you use them wrong.

    David Cressey
"Elvis K. Ing" <> wrote in message

> Hello everyone,
> I am about to design a RDB, and would like to hear your opinions regarding
> design issues.
> Basically, the DB will be the backend for a web based contact management
> For each contact, lots of information (first name, surname, address) will
have to
> be stored. Many of these fields are optional values.
> First question: How would you design the relations? Have distinct
relations for
> each of these optional attributes, at the cost of a lot of joins? Or would
> stuff all closely related information in one relation and put up with NULL
> for some of the attributes?
> Furthermore, each contact in the database can be one of several types,
> these small investors, institutionals, journalists. Each type might
require some
> additional information to be stored, e. g. market segment, industry.
> there are some intersections among these types. As an example, the
> attribute might apply to financial analysts and institutional investors,
but not
> for small investors or journalists.
> Question: How would you design these "contact classes" in a relational
model? I
> think that there should be only one relation for each concept like market
> or industry, as opposed to having a relation for additional journalist and
> additional investor attributes and having intersections among their
> Which actions could be taken to keep the design as flexible as possible?
Maybe I
> will have to add further "contact classes" in the future, or add
> attributes for a certain class. It might also happen that the domains for
some of
> the "common" attributes differ, depending on the "contact class".
> Thanks a lot for your opinions, any hints or starting points. (-> Are
> similar design issues documented or described somewhere?)
> Elvis
> --
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Received on Wed Sep 05 2001 - 16:44:44 CEST

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