From: | Louis-David Mitterrand <vindex+lists-pgsql-sql(at)apartia(dot)org> |
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To: | "pgsql-sql(at)postgresql(dot)org" <pgsql-sql(at)postgresql(dot)org> |
Subject: | Re: check constraint on multiple tables? |
Date: | 2010-03-03 16:06:59 |
Message-ID: | 20100303160659.GA22889@apartia.fr |
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Lists: | pgsql-sql |
On Wed, Mar 03, 2010 at 10:03:05AM -0600, Little, Douglas wrote:
> Hello,
>
> I would have designed as ship > cabin (PK of ship_id, Cabin_id)
> And a separate chain of cabin_type > cabin_category > cabin
Ah, now I'm having second thoughts about my schema ;)
> Type, and category are group classifiers and shouldn't be used to
> define the uniqueness of a cabin.
Yes, but some ships have quite unique cabin types and categories.
> Take an example where the cabin category and type are defined globally
> for the entire fleet. Currently you'll have to duplicate the type,
> category defintions for each ship.
Each ship is unique (more or less, a cruise line has several classes of
ships). So are its types and cats so it's not so clear cut.
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