From: | Richard Broersma <richard(dot)broersma(at)gmail(dot)com> |
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To: | pgsql-sql(at)postgresql(dot)org |
Subject: | Re: check constraint on multiple tables? |
Date: | 2010-03-03 15:57:48 |
Message-ID: | 396486431003030757q115b977lde82c4bf443f4b0d@mail.gmail.com |
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Lists: | pgsql-sql |
On Wed, Mar 3, 2010 at 7:38 AM, Louis-David Mitterrand
<vindex+lists-pgsql-sql(at)apartia(dot)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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