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help / color / mirror / Atom feedFrom: Bruce Momjian <[email protected]>
To: Robert Haas <[email protected]>
Cc: Grzegorz Szpetkowski <[email protected]>
Cc: [email protected]
Subject: Re: 5.3.5. Foreign Keys (The SQL Language) possible enhance
Date: Wed, 12 Oct 2011 16:59:04 -0400 (EDT)
Message-ID: <[email protected]> (raw)
In-Reply-To: <[email protected]>
Robert Haas wrote:
> On Fri, May 6, 2011 at 9:50 PM, Grzegorz Szpetkowski
> <[email protected]> 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.
Done with the attached patch.
--
Bruce Momjian <[email protected]> http://momjian.us
EnterpriseDB http://enterprisedb.com
+ It's impossible for everything to be true. +
Attachments:
[text/x-diff] /rtmp/null (660B, 2-%2Frtmp%2Fnull)
download | inline diff:
diff --git a/doc/src/sgml/ddl.sgml b/doc/src/sgml/ddl.sgml
new file mode 100644
index c624fc2..ea840fb
*** a/doc/src/sgml/ddl.sgml
--- b/doc/src/sgml/ddl.sgml
*************** CREATE TABLE orders (
*** 688,694 ****
quantity integer
);
</programlisting>
! Now it is impossible to create orders with
<structfield>product_no</structfield> entries that do not appear in the
products table.
</para>
--- 688,694 ----
quantity integer
);
</programlisting>
! Now it is impossible to create orders with non-NULL
<structfield>product_no</structfield> entries that do not appear in the
products table.
</para>
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To: [email protected]
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Subject: Re: 5.3.5. Foreign Keys (The SQL Language) possible enhance
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