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Message-ID: <20061023154116.86160.qmail@web31812.mail.mud.yahoo.com>
Date: Mon, 23 Oct 2006 08:41:16 -0700 (PDT)
From: Richard Broersma Jr <rabroersma@yahoo.com>
Subject: Re: delete on cascade
To: Luca Ferrari <fluca1978@infinito.it>, pgsql-sql@postgresql.org
In-Reply-To: <200610231049.16507.fluca1978@infinito.it>
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> Hi all,
> I guess this is an already asked question, but I didn't found an answer, so 
> apologize me. Imagine I've got two tables:
> skill(id,description)		// primary key => id
> family(id,description)	// primary key => id
> and I want to associate skills to families:
> ass_sf(id_skill,id_family)	// appropriate foreign keys
> 
> Tables are already created and the database is running. Now I'd like to 
> implement a delete cascade, thus when I delete a skill also its association 
> with the family must be deleted. I gues I should have declared the skill 
> table as follows:
> CREATE TABLE skill
> (
> 	id varchar(20) on delete cascade,
> 	description varchar(50),
> 	primary key(id)
> );
> 
> right? The problem is: how can I alter the table to add the column constraint 
> now, without redeclaring the table?
> Thanks very much for helping me.

This link has one line that is very similar to what you want to do.  You will probably have to
start a transaction, drop the foriegn key contraint and then add a new foriegn key contraint with
the on drop cascade .

http://archives.postgresql.org/pgsql-general/2006-10/msg00467.php

Regards,

Richard Broersma Jr.