This right join query is too slow

Question

My query of interest is below

    SELECT COUNT(a.id) 
      FROM users AS a 
RIGHT JOIN date_log AS b 
        ON a.id = b.user_id 
     WHERE
           b.meeting_date BETWEEN '2012-06-01' 
                      AND DATE_ADD('2012-06-01', INTERVAL 1 MONTH) 
  GROUP BY a.id

However, it's too slow when I try to select data from a large database. I added 'group by' terms in the query for removing duplicated ids.

Is there better way to do this job?

Answer 1

First check you have indexes setup for date_log.user_id and meeting_date.

Then have you considdered using 'distinct' instead of group?

Select count(distinct a.id)

Answer 2

If you just need the count, you can make this query a left-join, and see if MySQL has a better time executing it (I'm not sure how it actually performs RIGHT JOINs, but I can imagine it in ways which are inefficient compared to LEFTs...

SELECT users.id, count(users.id) as user_count
FROM 
  date_log
  LEFT JOIN users ON date_log.user_id = users.id
WHERE
  date_log.meeting_date BETWEEN '2012-06-01' AND DATE_ADD('2012-06-01', INTERVAL 1 MONTH)
GROUP BY users.id