平均值的最大值

Question

我应该获得每个部门的平均工资，并且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。有人知道吗？

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

我收到此错误：第1行出现错误：ORA-00937：不是单组组函数

Answer 1

没有CTE，您可以执行以下操作：

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

通过谷歌搜索...

原因：SELECT 列表不能同时包含组函数（例如 AVG、COUNT、MAX、MIN、SUM、STDDEV 或 VARIANCE）和单个列表达式，除非单个列表达式包含在 GROUP BY 子句中。

操作：从 SELECT 列表中删除组函数或单个列表达式，或者添加包含列出的所有单个列表达式的 GROUP BY 子句。