Re: Foreign Unique Constraint

From: chester c young <chestercyoung(at)yahoo(dot)com>
To: Jon Horsman <horshaq(at)gmail(dot)com>
Cc: sql pgsql <pgsql-sql(at)postgresql(dot)org>
Subject: Re: Foreign Unique Constraint
Date: 2007-03-27 17:35:37
Message-ID: 415536.67726.qm@web54310.mail.yahoo.com
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>
> create table table1 (
> id SERIAL PRIMARY KEY
> extension UNIQUE,
> <other fields>
> )
>
> create table table2 (
> id SERIAL PRIMARY KEY
> extension UNIQUE,
> <different fields>
> )
>
> Basically table 1 and table 2 both have the concept of an extension
> that must be unique but the rest of the info in the tables are
> different. I need to ensure that if i add an entry to table 1 with
> extension 1000 that it will fail if there is already an entry in
> table2 with the same extension.

use a pre-insert triggers - one for each table. include something like

if exists( select 1 from table2 where extension=new.extension ) then
raise exception ...
end if;


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