从子查询返回多个列时如何只使用一列？

Question

假设我有一个像

这样的子查询

select deptNo, count(*) 
from employee group by deptNo

我想在主查询中使用count（*），我该怎么做？

例如：count(*) in (select deptNo, count(*) from employee group by deptNo)之类的查询; 或者做什么的替代方案？

Answer 1

select avg(cnt) 
from (
    select deptNo, count(*) as cnt
    from employee group by deptNo) src

Answer 2

select t.count1  from 
(select deptNo,count(*) as count1 from employee group by deptNo) as t

尝试在内部查询中使用别名来计算。我假设您只需要列count1。（我已将列命名为count1）