如何显示department_id，job_id和每个部门中每个工作分类的平均工资？

Question

我都试过，但显然它只会给MT的平均工资为所有的部门不是每个职业分类

SELECT e.department_id, e.job_id, (SELECT avg(salary) 
            FROM employees) 
FROM employees e 
GROUP BY department_id, job_id; 

Answer 1

我想你想这个（如果你的目标是获得几个部门标识/ JOB_ID平均工资） ：

SELECT e.department_id, e.job_id, avg(e.salary) 
FROM employees e 
GROUP BY e.department_id, e.job_id; 

如果你想只平均为部门标识，你可以写：

SELECT e.department_id, e.job_id, 
    (SELECT avg(e1.salary) 
    FROM employees e1 
    where e1.department_id = e.department_id) 
FROM employees e 
GROUP BY e.department_id, e.job_id; 

Answer 2

你想该部门的平均薪水是多少？做一个相关的子查询：

SELECT e.department_id, e.job_id, (SELECT avg(salary) 
            FROM employees e2 
            where e2.department_id = e.department_id) 
FROM employees e