From: Richard Broersma <richard.broersma@gmail.com>
To: pgsql-sql@postgresql.org
Subject: Re: check constraint on multiple tables?
Date: Wed, 3 Mar 2010 07:57:48 -0800
Message-ID: <396486431003030757q115b977lde82c4bf443f4b0d@mail.gmail.com> (raw)
In-Reply-To: <20100303153831.GA20503@apartia.fr>
References: <20100303150227.GA18661@apartia.fr>
<396486431003030714s48b239e2ub8b58a49b9aa29e4@mail.gmail.com>
<20100303151900.GA19735@apartia.fr>
<396486431003030729x17f921bcr7ff439113a5644ab@mail.gmail.com>
<20100303153831.GA20503@apartia.fr>
On Wed, Mar 3, 2010 at 7:38 AM, Louis-David Mitterrand
<vindex+lists-pgsql-sql@apartia.org> wrote:
> Each ship is different and has specific cabin types and categories. Of
> course there is some overlap between ships but I thought it simpler (or
> more elegant) to use that hierarchy. Maybe my schema is wrong?
I'm probably ignorant about ships, but are ships like air planes in
that all ships belong to a similar class/construction? i.e. all
Bowing 747 are essentially configured that same. Can you define ship
classes that each ship belongs? You describe cabin_category as if it
is actually an area of this ship, would all ships of a class have
nearly identical ship_areas/cabin_categories?
> I could add an id_ship to 'cabin' but that would make two (potentialy
> conflicting) relations to 'ship'.
It true that more refinement is necessary. As you've mentioned that
this hierarchy will have overlap, this is an indication of a violation
of the second normal form (I believe).
--
Regards,
Richard Broersma Jr.
Visit the Los Angeles PostgreSQL Users Group (LAPUG)
http://pugs.postgresql.org/lapug
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To: pgsql-sql@postgresql.org
Cc: richard.broersma@gmail.com
Subject: Re: check constraint on multiple tables?
In-Reply-To: <396486431003030757q115b977lde82c4bf443f4b0d@mail.gmail.com>
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