Date: Tue, 11 Dec 2007 16:42:46 -0300
From: Alvaro Herrera <alvherre@alvh.no-ip.org>
To: PostgreSQL Admin <postgres@productivitymedia.com>
Cc: pgsql-sql@postgresql.org
Subject: Re: Foreign Key for multi PK or design question
Message-ID: <20071211194246.GK10710@alvh.no-ip.org>
References: 
 <863ECFDF04C8804ABDF3559D87F157C638E5D9@MAGPTCPEXC02.na.mag-ias.net>
	<475ED504.7080006@productivitymedia.com>
	<20071211185330.GA16159@a-kretschmer.de>
	<475EE126.5030302@productivitymedia.com>
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PostgreSQL Admin wrote:
> This is my layout so far:
> 
> CREATE TABLE users (
> id serial NOT NULL,
> --question REFERENCES questions(id) ON DELETE CASCADE ## ON REMOVED##
> );
> 
> CREATE TABLE questions (
> id serial NOT NULL,
> questions varchar(450) NOT NULL
> );
> 
> CREATE TABLE answers (
> id serial NOT NULL,
> question_id int REFERENCES questions(id) ON DELETE CASCADE,
> user_id int REFERENCES users(id) ON DELETE CASCADE,
> answer varchar(450) NOT NULL,
> created timestamptz NOT NULL
> );
> 
> Originally I wanted to have a foreign key that would be the pk of the
> question table.  So if the user answered Q2, 5 and 6 - the user.fk would
> store values 2,5,6 - but I have passed most of logic to the answer table.

That would have made no sense.

> Does this look correct? or most efficient?

Yeah it seems sane, however you have forgotten to add NOT NULL to the FK
fields.

-- 
Alvaro Herrera                               http://www.PlanetPostgreSQL.org/
"No me acuerdo, pero no es cierto.  No es cierto, y si fuera cierto,
 no me acuerdo."                 (Augusto Pinochet a una corte de justicia)