Volkan YAZICI escreveu:
Mike Ginsburg <mginsburg@xxxxxxxxxxxxxxxxxxxxxxx> writes:
There is probably a really simple solution for this problem, but for
the life of me I can't see to think of it. I have three tables
--contains u/p for all users in the site
TABLE users (user_id INT primary key, username VARCHAR(50), password TEXT)
--list of all possible events (login, logout, timeout)
TABLE events (event_id INT primary key, event VARCHAR(255))
--logs the activity of all users logging in/out, etc
TABLE log (log_id INT primary key, user_id INT REFERENCES users,
event_id INT REFERENCES event);
How would I query to find out which user has the most activity?
SELECT user_id, COUNT(event_id)
FROM log
GROUP BY (user_id)
HAVNG COUNT(event_id) = ???
SELECT user_id, max(count(event_id))
max(count() is invalid.
aggregate function calls may not be nested
FROM log
GROUP BY user_id;
or
SELECT user_id, count(event_id)
FROM log
GROUP BY user_id
ORDER BY count(event_id) DESC
LIMIT 1;
If more than 1 user has the most activity only one is listed.
Try:
SELECT user_id, COUNT(event_id)
FROM log
GROUP BY (user_id)
HAVING COUNT(event_id) = (SELECT max(l.ct) FROM
(SELECT count(event_id) AS ct FROM log GROUP BY user_id) AS l)
ORDER BY user_id;
Osvaldo
