SELECT concat(YEAR, '-', lpad(MONTH, 2, '0')) AS MONTH,
                               COUNT(id) AS COUNT
                        FROM
                          (SELECT id,
                                  email,
                                  EXTRACT(MONTH FROM joined) AS MONTH,
                                  EXTRACT(YEAR FROM joined) AS YEAR
                           FROM
                             (SELECT id,
                                     email,
                                     MIN("from") AS joined
                              FROM
                                (SELECT members."id",
                                        members."email",
                                        fees."from",
                                        fees. "to"
                                 FROM members,
                                      fees
                                 WHERE members.id = member_id
                                   AND fees."from" BETWEEN ? AND ?) tbl
                              GROUP BY id) AS tbl2) tbl3
                        GROUP BY concat(MONTH, YEAR);


# ERROR:  COLUMN "tbl.email" must appear IN the GROUP BY clause OR be used IN an aggregate FUNCTION
# LINE 12:              email,
#                       ^