在嵌套子查询中分组

Question

我有两张桌子：

Researcher (ResId, Fname, Gname)
Book (bookID, ResID*, Descr)

我需要使用IN（我的任务条件之一）声明来显示超过5本书的研究人员名单。

我得到了以下似乎是逻辑的SQL查询，但它给出了错误。子查询本身就可以正常工作：

select  ResId, Fname
from Researcher
where ResId in
   (select Book.ResId, count(*)
   from Book
   group by Book.ResId
   having count(*) > 5
   )

Answer 1

这是否按预期工作？

Select  ResId, Fname
From Researcher r
Inner Join Book b on b.ResId = r.ResId
Group By r.ResId, r.FName
Having count(b.*) > 5

Answer 2

where ResId in
   (select Book.ResId, count(*)

使用IN (Select...时，您只能在子查询中选择一列 将上述内容更改为：

where ResId in
   (select Book.ResId

仅

Answer 3

只删除count(*)，如下所示：

select  ResId, Fname
from Researcher
where ResId in
   (select Book.ResId 
   from Book
   group by Book.ResId
   having count(*) > 5
   )