Problems using count() with a join
От | Igor Kryltsov |
---|---|
Тема | Problems using count() with a join |
Дата | |
Msg-id | cfrqke$1l1k$1@news.hub.org обсуждение исходный текст |
Список | pgsql-general |
Hi,I am using slightly modified example posted by Doug Younger and answered by Tom Lane :)(http://archives.postgresql.org/pgsql-sql/1999-08/msg00159.php) I have the following 2 tables: Table groups: g_id int4 g_name text Table users: u_id int4 g_id int4 u_act int4 0 - value means "Inactive" and 1 - value means "Active" (used instead of boolean type for DB interoperability :) ) What I want is to get a count of users in each group with count of active users in each group, even if there are no users in the group. This example gives a count of users in each group: SELECT t1.g_name,count(t2.g_id) as users_count FROM groups t1,users t2 WHERE t1.g_id = t2.g_id GROUP BY t1.g_name;If you can help to modify it to output --> g_name, users_count, active_users_count So it could be:Group_A | 89 | 34Group_B | 75 | 75Group_C | 25 | 0 <-- all users are inactive hereGroup_D | 0 | 0 <---- Assume that this is a result of UNION which will add groups without employeesThank you,Igor
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