I need a help in writing a query. I have data as follows: mydb=# select * from usrlog ; logid | userid | loginhr | logouthr -------+----------+---------+---------- 0 | sburnwal | 0 | 1 1 | rickyrs | 1 | 5 2 | satishbn | 1 | 6 3 | taohujin | 2 | 4 4 | jospehm | 4 | 5 Table captures the login and logout time (taking hour here to simplify) of users and my aim to find the number of logged-in users (online users) at every hr (1st hr i.e. 0-1, 2nd hrs i.e. 1-2, 3rd hr i.e. 2-3 and ... so on). As the data indicates, use is not logging out in same hr as hr of login. A user can be logged-in for more than one hr. For example, here user rickyrs is logged-in for 1st, 2nd, 3rd, 4th and 5th hr. My query needs to find out in the last 24 hrs, how many users were logged-in at each hr. I want the result this way: Nth-hr user --------------------------- 1 sburnwal 2 rickyrs 2 satishbn 3 rickyrs 3 satishbn 3 taohujin 4 rickyrs 4 satishbn 4 taohujin 4 josephm Appreciate your response in advance. For me, even the count of users on hourly basis is fine. Thanks -Satish -- Sent via pgsql-general mailing list (pgsql-general@xxxxxxxxxxxxxx) To make changes to your subscription: http://www.postgresql.org/mailpref/pgsql-general