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Re: mutually exclusive subtypes

From: "Daniel T(dot) Staal" <DStaal(at)usa(dot)net>
To: pgsql-novice(at)postgresql(dot)org
Subject: Re: mutually exclusive subtypes
Date: 2006-04-13 15:23:28
Message-ID: 59083.63.172.115.138.1144941808.squirrel@MageHandbook.com (view raw or flat)
Thread:
Lists: pgsql-novice
On Thu, April 13, 2006 11:08 am, Olinga K. Abbott said:

> Of course, being an airplane and being an automobile are mutually
> exclusive. How does one program the mutual exclusivity in PostgreSQL?
> I've studied using check contraints, triggers, and rules, but I'm not
> finding any obvious way to program this.

The obvious thing to me would be inheritance.  Both 'auto' and 'airplane'
are tables that inheret from the same table.  I'm not sure if 'unique'
holds across subtables, (I'm guessing it probably does, if it is in the
main table) but if it doesn't it would be fairly easy to write a procedure
that checks for the relevent entries in the top level table and all it's
children before entering data.

Daniel T. Staal

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