Re: Data Model - Please Comment on my Approach

From: Dieter Nöth <dnoeth_at_gmx.de>
Date: Sat, 24 May 2003 10:06:32 +0200
Message-ID: <ban989$1g1i6$1_at_ID-28204.news.dfncis.de>


Karsten Farrell wrote:

>>The rest of your design is a meta-data
>>model, with column descriptions.  You will wind up with monster joins.
>> Sorry, but this is not a good idea at all.  The original model is
>>correct.

>
> Well, I have two comments:
>
> 1. There is nothing wrong with joins. They are a part of life in the
> RDBMS world. You normally eliminate many of them when you build a Data
> Warehouse, but ONLY then. One of the most common type of joins is done
> to "convert" (display) a code to its description (they're called lookup
> tables, for obvious reasons).
>
> 2. The original model is not even first normal form (1NF), but is
> reminiscent of the flat-file databases of the 1970s. Normally you try to
> get your model to at least 3NF. To get to 1NF, you eliminate all the
> column "arrays" - even though they're not called that in a table. The
> reason the original model is flawed becomes obvious when someone decides
> to breakdown age brackets into smaller (or larger) groups than the
> current 5-year groups ... or they want to capture other income levels
> .... or they want to toss in another house type. If you have stored
> nothing but totals, you'll have no way to determine which of the tens or
> thousands now fall into the split/joined categories.

I like that.
Advising Joe Celko about Joins, Normal Forms, Flat files ;-))

Dieter Received on Sat May 24 2003 - 10:06:32 CEST

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