From: David Pradier <david.pradier@clarisys.fr>
To: Daryl Richter <daryl@brandywine.com>
Cc: Russell Simpkins <russellsimpkins@hotmail.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Design problem : using the same primary keys for inherited objects.
Date: Mon, 17 Oct 2005 15:56:05 +0200
Message-ID: <20051017135605.GD19930@clarisys.fr> (raw)
In-Reply-To: <434FC756.90901@brandywine.com>
References: <20051014091829.GB19930@clarisys.fr>
<BAY103-DAV1541E0C0650CC9BDA28204B57D0@phx.gbl>
<20051014124334.GC19930@clarisys.fr>
<434FC756.90901@brandywine.com>
> >I give a clearer example :
> >CREATE TABLE actor (
> >id_actor serial PRIMARY KEY,
> >arg1 type1,
> >arg2 type2
> >)
> >CREATE TABLE person (
> >id_person INTEGER PRIMARY KEY REFERENCES actor,
> >arg3 type3,
> >arg4 type4
> >)
> >Don't you think it is a BAD design ?
> >If it isn't, well, it will expand my database practices.
>
> It *is* a bad design. You should not do this. After all, how is that
> any different than this?
> CREATE TABLE actor_person (
> id_actor serial PRIMARY KEY,
> arg1 type1,
> arg2 type2
> arg3 type3,
> arg4 type4
> )
> Furthermore, inheritance is almost certainly the wrong relationship type
> here. Normally, Actor would be a Role that a Person would be playing:
Oups, I've made a vocabulary mistake.
By 'actor', I meant "somebody who does something". Lots of tables inherits
from 'actor' in our current design, each of these being a "job" :
laboratory, delivering company, etc...
Furthermore, 'person' inherits from 'actor', and some other tables inherits
from 'person' : user, physician, customer, etc...
Do you continue to think that inheritance is the wrong relationship type
here ?
> It *is* a bad design. You should not do this. After all, how is that
> any different than this?
Well, not every line of actor are in laboratory, as some are in person,
and in some moreother tables. So, it is different, isn't it ?
--
David Pradier -- Directeur Technique de Clarisys Informatique -- Chef de projet logiciels libres / open-source
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To: pgsql-sql@postgresql.org
Cc: david.pradier@clarisys.fr, daryl@brandywine.com, russellsimpkins@hotmail.com
Subject: Re: Design problem : using the same primary keys for inherited objects.
In-Reply-To: <20051017135605.GD19930@clarisys.fr>
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