关联复合查询怎么写
开源系统 更新 2019-03-02 11:52:56
迅睿粉丝
迅睿粉丝
关联复合查询怎么写，例如下面这样：
select a.*,b.* from dr_book a
left join
(select book_id,count(*) as student_num from dr_student_video group by book_id) b
on a.id=b.book_id
