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Date: Thu, 23 Jul 2009 04:23:29 -0400
Message-ID: <bd36f99e0907230123w755f0efclf36c6bb303b9fcbd@mail.gmail.com>
Subject: Re: Need magical advice for counting NOTHING
From: Glenn Maynard <glenn@zewt.org>
To: pgsql-sql <pgsql-sql@postgresql.org>
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On Thu, Jul 23, 2009 at 1:01 AM, Andreas<maps.on@gmx.net> wrote:
> SELECT user_name, log_type_fk, COUNT(log_type_fk)
> FROM log
> JOIN users ON (user_id =3D user_fk)
> WHERE (ts IS BETWEEN =C2=A0sometime =C2=A0AND =C2=A0 another)
> GROUP BY user_name, log_type_fk
> ORDER BY user_name, log_type_fk

create table users (user_id integer, user_name varchar);
create table log_type  (log_type_id integer, log_type integer);
create table log (log_id integer, log_type_fk integer, user_fk integer);
insert into log_type (log_type_id, log_type) values (1, 1);
insert into log_type (log_type_id, log_type) values (2, 2);
insert into users (user_id, user_name) values (1, 'a');
insert into users (user_id, user_name) values (2, 'b');
insert into log (log_id, log_type_fk, user_fk) values (1, 1, 1);
insert into log (log_id, log_type_fk, user_fk) values (2, 2, 1);
insert into log (log_id, log_type_fk, user_fk) values (3, 2, 1);
insert into log (log_id, log_type_fk, user_fk) values (4, 1, 2);

SELECT user_name, log_type.log_type, sum((log_type_fk IS NOT
NULL)::integer) AS count
FROM users JOIN log_type ON (true) LEFT JOIN log ON (user_id =3D user_fk
AND log.log_type_fk =3D log_type.log_type)
GROUP BY user_name, log_type.log_type
ORDER BY user_name, log_type.log_type;


 user_name | log_type | count
-----------+----------+-------
 a         |        1 |     1
 a         |        2 |     2
 a         |        3 |     0
 b         |        1 |     1
 b         |        2 |     0
 b         |        3 |     0

--=20
Glenn Maynard