SQL如何从另一个表中不存在的表中选择

Question

For example i have 2 tables that have relationship with one another. room_directory.id and booked_room.room_id

room_directory

id
room_number

booked_room

id
booking_id
room_id

How to write query that select only the rooms from room_directory that are not exists in booked_room table?

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);

要么

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