sql - 平均值的最大值

Question

我应该得到每个部门的平均工资，只显示平均工资最高的部门。我想出了这个查询，但它不起作用。有人有什么想法吗？

SELECT department, max(avg(wage))
FROM employees
GROUP BY department;

我收到此错误：第 1 行的错误：ORA-00937：不是单组组函数

Answer 1

如果没有 CTE，您可以：

Select Z.Department, Z.AvgWage
From  (
        Select Department, Avg(Wage) AvgWage
        From Employees
        Group By Department
        ) As Z
Where AvgWage = (
                Select Max(Z1.AvgWage)
                From    (
                        Select Department, Avg(Wage) AvgWage
                        From Employees
                        Group By Department
                        )  Z1
                )

使用 CTE，您可以：

With AvgWages As
    (
    Select Department
        , Avg(Wage) AvgWage
        , Rank() Over( Order By Avg(Wage) Desc ) WageRank
    From Employees
    Group By Department
    )
Select Department, AvgWage, WageRank
From AvgWages
Where WageRank = 1

Answer 2

这个工作：

select *
from
(
  SELECT 
      department
      , avg(wage) as ave_wage
  FROM employees 
  GROUP BY department
)x 
order by ave_wage desc 
where rownum < 2;

（免责声明：完全未经测试，所以我可能将 rownum 位放在了错误的位置）

Answer 3

尽管下面的查询显示与其他答案相同的结果，但很高兴向用户展示如何作为替代方法完成：

--Method 1 (Davek's select of 1st row over Order by) Brilliant!
--Method 2 (Thomas' where = sub-query result)
--Method 3 (Thomas' based on ranking)

--Method 4 (Inner join sub-queries)
select distinct a.department, a.wage from 
         (select distinct department, AVG(wage) as wage from employees group by department) as a
   inner join 
         (select Max(wage) as wage from
                (select distinct department, AVG(wage) as wage from employees group by department) as x) as b
   on a.wage = b.wage 
where a.wage = b.wage 

--Method 5 (AVG wage in (sub-query))
select distinct a.department, a.wage
from (select distinct department, AVG(wage) as wage from employees group by department) as a
Where a.wage in 
    (select Max(wage) as wage from
        (select distinct department, AVG(wage) as wage from employees group by department) as x)

也期待看到此选择的自定义功能:)

Answer 4

通过谷歌搜索...

原因：一个 SELECT 列表不能同时包含一个组函数，例如 AVG、COUNT、MAX、MIN、SUM、STDDEV 或 VARIANCE，以及​​一个单独的列表达式，除非单独的列表达式包含在 GROUP BY 子句中。

行动：从 SELECT 列表中删除组函数或单个列表达式，或添加一个 GROUP BY 子句，其中包括列出的所有单个列表达式。