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explain
select * from (
select 1 as foo from sakila.actor as actor_1
cross join sakila.actor as actor_2
) as x
inner join (
select 1 as foo from sakila.actor as actor_3
cross join sakila.actor as actor_4
) as y using (foo);
+----+-------------+------------+-------+---------------+---------+---------+------+-------+-------------+
| id | select_type | table | type | possible_keys | key | key_len | ref | rows | Extra |
+----+-------------+------------+-------+---------------+---------+---------+------+-------+-------------+
| 1 | PRIMARY | <derived2> | ALL | NULL | NULL | NULL | NULL | 40000 | |
| 1 | PRIMARY | <derived3> | ALL | NULL | NULL | NULL | NULL | 40000 | Using where |
| 3 | DERIVED | actor_3 | index | NULL | PRIMARY | 2 | NULL | 200 | Using index |
| 3 | DERIVED | actor_4 | index | NULL | PRIMARY | 2 | NULL | 200 | Using index |
| 2 | DERIVED | actor_1 | index | NULL | PRIMARY | 2 | NULL | 200 | Using index |
| 2 | DERIVED | actor_2 | index | NULL | PRIMARY | 2 | NULL | 200 | Using index |
+----+-------------+------------+-------+---------------+---------+---------+------+-------+-------------+
|
