CREATE TABLE `test`.`t1` ( `id` int(11) NOT NULL AUTO_INCREMENT, `val` bit(1) NOT NULL DEFAULT b'0', PRIMARY KEY (`id`,`val`) ) ENGINE=InnoDB AUTO_INCREMENT=122 DEFAULT CHARSET=utf8mb4; INSERT INTO test.t1 (val) VALUES (0),(1); INSERT INTO test.t1 (val) SELECT val FROM test.t1 ; INSERT INTO test.t1 (val) SELECT val FROM test.t1 ; explain select * from `test`.`t1` WHERE (`id` = '123' AND `val` = '1') ; select * from `test`.`t1` WHERE (`id` = '123' AND `val` = '1') ; select count(*) from `test`.`t1`; explain delete from `test`.`t1` WHERE (`id` = '123' AND `val` = '1') ; delete from `test`.`t1` WHERE (`id` = '123' AND `val` = '1') ; select count(*) from `test`.`t1`; drop table `test`.`t1`;