SQL查询帮助 - 查找没有关系的行

Question

考虑一个带有Client表和Book表的数据库：

客户：person_id

书籍：book_id

Client_Books：person_id，book_id

你怎么能找到所有没有书籍的人ID？ （不进行外连接并寻找空值）

Answer 1

select * 
from Client  as c
where not exists(select * from Client_Books where person_id =c.person_id ) 

Answer 2

select *
from Client 
where person_id not in (select person_id from Client_Books)

Answer 3

SELECT * FROM Client WHERE person_id not in (SELECT person_id FROM Client_Books)

Answer 4

select *  
from Client as c 
where (select coun(*) from Client_Books where person_id =c.person_id ) = 0

COUNT表示完整性，因为已经发布了EXISTS和IN解决方案。