MySQL 에서는 MINUS 가 안되는 군요
-- NOT EXISTS -- SELECT room_number FROM 룸_테이블 m WHERE NOT EXISTS (SELECT 1 FROM 예약_테이블 WHERE start_date < 종료일 AND end_date > 시작일 AND room_number = m.room_number ) ; -- NOT IN -- SELECT room_number FROM 룸_테이블 WHERE room_number NOT IN (SELECT room_number FROM 예약_테이블 WHERE start_date < 종료일 AND end_date > 시작일 ) ; -- OUTER JOIN & IS NULL -- SELECT m.room_number FROM 룸_테이블 m LEFT OUTER JOIN 예약_테이블 s ON s.start_date < 종료일 AND s.end_date > 시작일 AND s.room_number = m.room_number WHERE s.room_number IS NULL ;