mysql> explain  select ac,src,dst,sum(bytes),sum(packets),srcuser,dstuser from data where stamp > '2006-08-23 01:00:00' group by hash                                                     -> ;                                                                                                                                                                              +----+-------------+-------+-------+---------------+---------+---------+------+---------+-------------+                                                                               | id | select_type | table | type  | possible_keys | key     | key_len | ref  | rows    | Extra       |
+----+-------------+-------+-------+---------------+---------+---------+------+---------+-------------+
|  1 | SIMPLE      | data  | index | stamp         | PRIMARY | 16      | NULL | 5339637 | Using where | 
+----+-------------+-------+-------+---------------+---------+---------+------+---------+-------------+
1 row in set (0.06 sec)