MYSQL mag einen Join, braucht aber nur die neueste Zeile?

Sie können dies mit dem folgenden SQL tun:

SELECT name,
       (
        SELECT datecreated
          FROM tbl_comments
          WHERE tbl_users.user_id = tbl_comments.user_id
          ORDER BY datecreated LIMIT 1
       )
FROM tbl_users
WHERE category = '1';

ODER mit:

SELECT tbl_users.name, MAX(datecreated) AS latestcomment
  FROM tbl_users LEFT JOIN tbl_comments ON (tbl_users.user_id = tbl_comments.user_id)
  GROUP BY tbl_users.name;