id select_type table type possible_keys key key_len ref rows Extra
1 PRIMARY <derived2> system NULL NULL NULL NULL 1 "Using filesort"
1 PRIMARY <derived3> system NULL NULL NULL NULL 1
1 PRIMARY my_table ALL NULL NULL NULL NULL 32594440
3 DERIVED NULL NULL NULL NULL NULL NULL NULL "No tables used"
2 DERIVED NULL NULL NULL NULL NULL NULL NULL "No tables used"