+----+-------------+-------+------+-----------------------+---------+---------+--------------+---------+----------------------------------------------+
| id | select_type | table | type | possible_keys         | key     | key_len | ref          | rows    | Extra                                        |
+----+-------------+-------+------+-----------------------+---------+---------+--------------+---------+----------------------------------------------+
|  1 | SIMPLE      | s     | ALL  | NULL                  | NULL    | NULL    | NULL         |    3207 | Using where; Using temporary; Using filesort |
|  1 | SIMPLE      | p     | ref  | sid-pid,time,sid-time | sid-pid | 8       | sensors.s.id | 6467649 |                                              |
+----+-------------+-------+------+-----------------------+---------+---------+--------------+---------+----------------------------------------------+