| From: | "Sander Steffann" <sander(at)steffann(dot)nl> |
|---|---|
| To: | "Jeff Davis" <list-pgsql-hackers(at)empires(dot)org> |
| Cc: | "Hackers" <pgsql-hackers(at)postgresql(dot)org> |
| Subject: | Re: Why is MySQL more chosen over PostgreSQL? |
| Date: | 2002-08-03 17:33:04 |
| Message-ID: | 003201c23b13$d3091380$64c8a8c0@balefire10ww |
| Views: | Whole Thread | Raw Message | Download mbox | Resend email |
| Thread: | |
| Lists: | pgsql-hackers |
Hi,
> > Well, if you also have soundcard_products, in your example you could
have a
> > product which is both a networkcard AND a soundcard. No way to restrict
> > that a product can be only one 'subclass' at a time... If you can make
that
> > restriction using the relational model, you can do the same as with
> > subclasses. But afaict that is very hard to do...
>
> CREATE VIEW networkcard_v AS SELECT * FROM products, networkcard WHERE
> products.id = networkcard.prod_id;
I think I was not clear enough... You just demonstrated that it is possible
to have a card that is a soundcard and a networkcard at the same time. The
point I tried to make was that it is difficult to _prevent_ this. Ofcourse I
agree with you that your example fits the relational model perfectly!
I have this problem in a few real-life cases, so if you have a sollution to
this, I would realy appreciate it!
Sander.
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