+------+-------------+------------+------+---------------+------+---------+------+--------+-----------------+
| id   | select_type | table      | type | possible_keys | key  | key_len | ref  | rows   | Extra           |
+------+-------------+------------+------+---------------+------+---------+------+--------+-----------------+
|    1 | PRIMARY     | <derived2> | ALL  | NULL          | NULL | NULL    | NULL | 188863 | Using where     |
|    1 | PRIMARY     | m          | ALL  | NULL          | NULL | NULL    | NULL | 205130 |                 |
|    2 | DERIVED     | a          | ALL  | NULL          | NULL | NULL    | NULL | 188863 | Using temporary |
+------+-------------+------------+------+---------------+------+---------+------+--------+-----------------+