SELECT useridfrom, count(*) as count
                            FROM mdl_message
                            WHERE useridto = 896
                                AND timeusertodeleted = 0
                                AND notification = 0
                            GROUP BY useridfrom
							
Empty set (0.00 sec)

+----+-------------+-------------+------+-----------------------------------------------------------------------+------------------------+---------+-------------------+------+----------------------------------------------+
| id | select_type | table       | type | possible_keys                                                         | key                    | key_len | ref               | rows | Extra                                        |
+----+-------------+-------------+------+-----------------------------------------------------------------------+------------------------+---------+-------------------+------+----------------------------------------------+
|  1 | SIMPLE      | mdl_message | ref  | mdl_mess_useusetimtim_ix,mdl_mess_usetimnot_ix,mdl_mess_usetimnot2_ix | mdl_mess_usetimnot2_ix | 18      | const,const,const |    1 | Using where; Using temporary; Using filesort |
+----+-------------+-------------+------+-----------------------------------------------------------------------+------------------------+---------+-------------------+------+----------------------------------------------+
1 row in set (0.00 sec)