Sql如何从另一个表中不存在的表中进行选择

Question

例如，我有2个彼此有关系的表。 room_directory.id 和 booked_room.room_id

room_directory

id
room_number

booked_room

id
booking_id
room_id

如何编写只选择 room_directory 中 registered_room 表中不存在的会议室的查询？

Answer 1

select * from room_directory where id not in (select room_id from  booked_room)

Answer 2

select * from room_directory r where r.id not in (select room_id from booked_room b where r.id = b.room_id);

或

SELECT * FROM room_directory r WHERE NOT EXISTS (SELECT * from booked_room b WHERE r.id = b.room_id);