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Re: BUG #2549: problem with NATURAL JOIN

From: Michael Fuhr <mike(at)fuhr(dot)org>
To: Kayteck <kayteck_master(at)o2(dot)pl>
Cc: pgsql-bugs(at)postgresql(dot)org
Subject: Re: BUG #2549: problem with NATURAL JOIN
Date: 2006-07-25 12:02:39
Message-ID: (view raw, whole thread or download thread mbox)
Lists: pgsql-bugs
On Tue, Jul 25, 2006 at 12:58:55AM +0000, Kayteck wrote:
> I have two tables joined by foreign key id_przelewu, and for some rows
> results of queries with NATURAL JOIN and JOIN ... USING (...) differs ! I've
> readed that NATURAL JOIN is only shorthand for the second method, but this
> results shows that's not true:
> select id_przelewu,id_zamowienia from zamowienia natural join przelew where
> id_klienta=4999;
>  id_przelewu | id_zamowienia 
> -------------+---------------
> (0 rows)

Do zamowienia and przelew have column names in common in addition
to id_przelewu?  NATURAL JOIN uses all common column names, not
just those specified in a foreign key constraint.

"Finally, NATURAL is a shorthand form of USING: it forms a USING
list consisting of exactly those column names that appear in both
input tables."

"NATURAL is shorthand for a USING list that mentions all columns
in the two tables that have the same names."

Michael Fuhr

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Subject: Re: BUG #2549: problem with NATURAL JOIN
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