mysql> explain select id
    -> from file
    -> where size in
    ->     (
    ->     select size from
    ->         (
    ->         select count(*) as c, size
    ->         from file
    ->         group by size
    ->         having c>1 and size>0
    ->         ) as t
    ->     );
+----+--------------------+------------+-------+---------------+----------+-----
----+------+-------+--------------------------+
| id | select_type        | table      | type  | possible_keys | key      | key_
len | ref  | rows  | Extra                    |
+----+--------------------+------------+-------+---------------+----------+-----
----+------+-------+--------------------------+
|  1 | PRIMARY            | file       | index | NULL          | filesize | 8
    | NULL | 21168 | Using where; Using index |
|  2 | DEPENDENT SUBQUERY | <derived3> | ALL   | NULL          | NULL     | NULL
    | NULL |  2813 | Using where              |
|  3 | DERIVED            | file       | index | NULL          | filesize | 8
    | NULL | 21168 | Using index              |
+----+--------------------+------------+-------+---------------+----------+-----
----+------+-------+--------------------------+
3 rows in set (0.01 sec)