mysql> explain select count(*) from cases c, cases_cstm cc WHERE c.status = 'Resolved' AND cc.case_source_c = 'email' AND c.resolution IS NULL;
+----+-------------+-------+------+-----------------+---------------+---------+-------------+-------+-------------+
| id | select_type | table | type | possible_keys   | key           | key_len | ref         | rows  | Extra       |
+----+-------------+-------+------+-----------------+---------------+---------+-------------+-------+-------------+
|  1 | SIMPLE      | c     | ref  | status,status_2 | status_2      | 27      | const,const |  7444 | Using where |
|  1 | SIMPLE      | cc    | ref  | case_source_c   | case_source_c | 9       | const       | 13956 | Using where |
+----+-------------+-------+------+-----------------+---------------+---------+-------------+-------+-------------+
2 rows in set (0.00 sec)