EXPLAIN EXTENDED SELECT * FROM C WHERE `int_key` IN (SELECT `int_nokey`);
id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY C ALL NULL NULL NULL NULL 20 Using where
Warnings:
Note 1276 Field or reference 'test.C.int_nokey' of SELECT #2 was resolved in SELECT #1
Note 1249 Select 2 was reduced during optimization
Note 1003 select `test`.`C`.`int_nokey` AS `int_nokey`,`test`.`C`.`int_key` AS `int_key` from `test`.`C` where (`test`.`C`.`int_nokey` = `test`.`C`.`int_key`)