Question

使用SQL查找A表,条件为A表中有但B表中没有的记录,A,B两表关联字段为id

这语句怎么写

Answer 1

select * from A where not exist select null from b where b.id=id
好像是这样写的
in 的开销比较大

Answer 2

select * from A where id not in (select id from B)