From: Luca Ferrari <fluca1978@infinito.it>
To: pgsql-sql@postgresql.org
Subject: delete on cascade
Date: Mon, 23 Oct 2006 10:49:16 +0200
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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.
Luca