help optimizing query
Hi all,
The situation: there are users in one table, and their access statistics
in the other. Now I want to find users whose last access time was more
than one month ago. As I've only had to write quite simple queries
involving no sub-selects so far, I'd like to ask your opinion if this
one scales at all or not.
SELECT u.login,last_use_time
FROM users u
JOIN (SELECT user_id, MAX(stop_time) AS last_use_time
FROM stats
GROUP BY user_id) AS s ON (u.id=s.user_id)
WHERE status='3' AND next_plan_id IS NULL
AND last_use_time < now() - interval '1 month'
ORDER BY last_use_time;
It seems to do the job, but how good is it in the long run? Any way I
could tweak it?
Thanks.
It seems to do the job, but how good is it in the long run? Any way I
could tweak it?
I think this form will work the best:
SELECT u.login, MAX(s.stop_time) AS last_use_time
FROM users u, stats s
WHERE u.id=s.user_id
AND u.status='3' AND u.next_plan_id IS NULL
GROUP BY u.login
HAVING MAX(s.stop_time) < (now() - interval '1 month')
ORDER BY last_use_time;
On Feb 9, 2008 8:04 PM, Adam Rich <adam.r@sbcglobal.net> wrote:
It seems to do the job, but how good is it in the long run? Any way I
could tweak it?I think this form will work the best:
SELECT u.login, MAX(s.stop_time) AS last_use_time
FROM users u, stats s
WHERE u.id=s.user_id
AND u.status='3' AND u.next_plan_id IS NULL
If only ba small number of fields have next_plan as null, an they
correlate to the status normally, then an index on state where
next_plan_id is null might help here.
Show quoted text
GROUP BY u.login
HAVING MAX(s.stop_time) < (now() - interval '1 month')
ORDER BY last_use_time;
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