Re: query with table alias

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Patrick Fiche
email : patrick.fiche@aqsacom.com
tél : 01 69 29 36 18
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-----Original Message-----
From: pgsql-general-owner@postgresql.org [mailto:pgsql-general-owner@postgresql.org]On Behalf Of Rodríguez Rodríguez, Pere
Sent: vendredi 12 novembre 2004 11:49
To: 'pgsql-general@postgresql.org'
Subject: [GENERAL] query with table alias

Hello,

I think I have found a query problem when the query has an alias for a table and use alias item and table name.

I ilustrate the problem with a simple table and query.

prr=# create table foo (c1 int2, c2 int2);
CREATE TABLE
prr=# insert into foo values (1, 1);
INSERT 301891 1
prr=# insert into foo values (2, 2);
INSERT 301892 1
prr=# select * from foo;
 c1 | c2
----+----
  1 |  1
  2 |  2
(2 filas)

prr=# select foo.c1, f.c2 from foo f;  -- >>> Incorrect result <<<
 c1 | c2
----+----
  1 |  1
  2 |  1
  1 |  2
  2 |  2
(4 filas)

prr=# explain select foo.c1, f.c2 from foo f; -- >>> Incorrect query plan <<<
                            QUERY PLAN
-------------------------------------------------------------------
 Nested Loop  (cost=20.00..20040.00 rows=1000000 width=4)
   ->  Seq Scan on foo f  (cost=0.00..20.00 rows=1000 width=2)
   ->  Materialize  (cost=20.00..30.00 rows=1000 width=2)
         ->  Seq Scan on foo  (cost=0.00..20.00 rows=1000 width=2)
(4 filas)

The result of the "select foo.c1, f.c2 from foo f" isn't correct, it do a cartesian product of foo table.

My version of PostgreSQL is PostgreSQL 7.4.5 on i386-pc-linux-gnu, compiled by GCC i386-linux-gcc (GCC) 3.3.4 (Debian 1:3.3.4-9).

Is this a bug?, is fixed in posteriors versions?

Thanks in advance,

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