From: Bruce Momjian <bruce@momjian.us>
Message-Id: <201109120209.p8C29kF13404@momjian.us>
Subject: Re: 5.3.5. Foreign Keys (The SQL Language) possible
 enhance
In-Reply-To: <BANLkTin1u+x6gnHq38W9dkmQyTh+24iqyA@mail.gmail.com>
To: Robert Haas <robertmhaas@gmail.com>
Date: Sun, 11 Sep 2011 22:09:46 -0400 (EDT)
CC: Grzegorz Szpetkowski <gszpetkowski@gmail.com>, pgsql-docs@postgresql.org
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Robert Haas wrote:
> On Fri, May 6, 2011 at 9:50 PM, Grzegorz Szpetkowski
> <gszpetkowski@gmail.com> wrote:
> > I have some remark about
> >
> > "Now it is impossible to create orders with product_no entries that do
> > not appear in the products table."
> >
> > http://www.postgresql.org/docs/9.0/static/ddl-constraints.html#DDL-CONSTRAINTS-FK
> [...]
> >
> > There is still possibility to add product_no (exactly NULL) value,
> > which does not appear (cannot because of primary key nature) in
> > products table. To get "full solution" you need create orders table as
> >
> > CREATE TABLE orders (
> > ? ?order_id integer PRIMARY KEY,
> > ? ?product_no integer REFERENCES products (product_no) NOT NULL,
> > ? ?quantity integer
> > );
> 
> I don't think we should change the example, but we could probably
> clarify the wording.

Any ideas on how to clarify the wording?

-- 
  Bruce Momjian  <bruce@momjian.us>        http://momjian.us
  EnterpriseDB                             http://enterprisedb.com

  + It's impossible for everything to be true. +