SELECT u.id AS ForUserId, nec.NumComments AS NumEntryComments, nic.NumComments AS NumImageComments
FROM users u

LEFT JOIN (
  SELECT e.user_id AS ForUserId, SUM(ce.NumComments) AS NumComments FROM entries e
  JOIN (
    SELECT entry_id, count(*) AS NumComments FROM `comments_entries` GROUP BY entry_id
  ) AS ce ON e.id = ce.entry_id
  GROUP BY ForUserId
) AS nec ON nec.ForUserId = u.id

LEFT JOIN (
  SELECT i.user_id AS ForUserId, SUM(ci.NumComments) AS NumComments FROM images i
  JOIN (
    SELECT image_id, count(*) AS NumComments FROM `images_comments` GROUP BY image_id
  ) AS ci ON i.id = ci.image_id
  GROUP BY ForUserId
) AS nic ON nic.ForUserId = u.id

WHERE u.status = 3

AND (nec.NumComments IS NOT NULL OR nic.NumComments IS NOT NULL);



/*
regular results:
+-----------+------------------+------------------+
| ForUserId | NumEntryComments | NumImageComments |
+-----------+------------------+------------------+
|         1 |               20 |               88 |
|        29 |             NULL |                3 |
|        61 |             NULL |                6 |
|        69 |             NULL |                6 |
+-----------+------------------+------------------+
4 rows in set (0.03 sec)


with SUM(nec.NumComments + nic.NumComments) AS NumComments:
+-----------+------------------+------------------+-------------+
| ForUserId | NumEntryComments | NumImageComments | NumComments |
+-----------+------------------+------------------+-------------+
|         1 |               20 |               88 |         108 |
+-----------+------------------+------------------+-------------+
1 row in set (0.00 sec)


with SUM(COALESCE(nec.NumComments,0) + COALESCE(nic.NumComments,0)) AS NumComments:
+-----------+------------------+------------------+-------------+
| ForUserId | NumEntryComments | NumImageComments | NumComments |
+-----------+------------------+------------------+-------------+
|         1 |               20 |               88 |         123 |
+-----------+------------------+------------------+-------------+
1 row in set (0.00 sec)


What the... it SUM'd all the rows together?!
*/