From: | "Nigel J(dot) Andrews" <nandrews(at)investsystems(dot)co(dot)uk> |
---|---|
To: | Rob Brown-Bayliss <rob(at)zoism(dot)org> |
Cc: | Andrew Sullivan <andrew(at)libertyrms(dot)info>, PostgreSQL General List <pgsql-general(at)postgresql(dot)org> |
Subject: | Re: Questions about my strategy |
Date: | 2002-07-31 10:47:35 |
Message-ID: | Pine.LNX.4.21.0207311129500.2710-100000@ponder.fairway2k.co.uk |
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Lists: | pgsql-general |
On 31 Jul 2002, Rob Brown-Bayliss wrote:
> On Wed, 2002-07-31 at 02:34, Andrew Sullivan wrote:
> > Why not three codes: model, colour, and size? Then you can query all
> > by model, and limit by size, colour, or both.
>
> How do you mean three codes?
>
> If you mean having more than one product code for a type of shoe thats
> what I am trying to avoid. I worked for acompany that did that a long
> time ago, the product was steel, and having 15 or more different lengths
> of a steel chanl meant having 15 product codes. It was often easier to
> walk out to the store and look for the product than to query each
> product code at the counter...
What Andrew is saying, I believe, is that you need to determine what defines a
shoe. What defines a shoe is it's model, it's size and it's colour. Therefore
you absolutely need a unique code to describe each variant. Either that or you
say the combination of (model, size, colour) is the unique code. Personally one
of the two designs I immediately thought of (the second one actually but the
first has more relations) that I would therefore consider strongly goes
something like:
shoe_model:
mid primary key,
name,
description,
manufacturer,
...
shoe_stock:
mid references shoe_model(mid),
colour,
size,
count
That structure gives you everything you want whether count is a difference or
an absolute, at least I think it does. I believe it's also more of a
correct solution than the convoluted way you seem to be thinking. Some database
expert will now correct me on those points. :)
--
Nigel J. Andrews
Director
---
Logictree Systems Limited
Computer Consultants
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