DROP TABLE test_table; CREATE TABLE `test_table` ( `id` int(11) NOT NULL AUTO_INCREMENT, `bool_field` bool NOT NULL DEFAULT false, PRIMARY KEY (`id`), KEY (bool_field,id) ) ENGINE INNODB; DROP PROCEDURE FILL_TABLE; DELIMITER $$ CREATE PROCEDURE FILL_TABLE() BEGIN DECLARE A INT; SET A=1; bucle: LOOP IF A > 5000 THEN LEAVE bucle; END IF; SET A = A + 1; INSERT INTO test_table VALUES (null,FLOOR(RAND()+.5)); END LOOP bucle; END$$ DELIMITER ; CALL FILL_TABLE; EXPLAIN EXTENDED SELECT id,bool_field FROM test_table WHERE bool_field IS FALSE; EXPLAIN EXTENDED SELECT id,bool_field FROM test_table WHERE bool_field = 0;