+----+--------------------+--------+--------+---------------+------------+---------+------

------+-------+-----------------------------+
| id | select_type        | table  | type   | possible_keys | key        | key_len | ref        | rows  | Extra                       |
+----+--------------------+--------+--------+---------------+------------+---------+------

------+-------+-----------------------------+
|  1 | PRIMARY            | a      | ALL    | NULL          | NULL       |    NULL | NULL       | 20531 | Using where; Using filesort |
|  1 | PRIMARY            | b      | eq_ref | PRIMARY       | PRIMARY    |       4 | func       |     1 | Using index                 |
|  2 | DEPENDENT SUBQUERY | photos | ref    | usernummer    | usernummer |       3 | users.a.id |     2 |                             |
+----+--------------------+--------+--------+---------------+------------+---------+------

------+-------+-----------------------------+
3 rows in set (0.00 sec)