MySQL平均值和总数

Question

这是我的代码，但所有值都是相同的。

SELECT 
    department.name, 
    AVG(salary) AS Average, 
    SUM(salary) AS Total
FROM 
    department, employee
GROUP BY 
    department.name

Answer 1

您错过了表格之间的加入条件，因此您将它们组合为完整的跨产品，而不是将员工仅链接到他们的部门。

SELECT d.name, AVG(e.salary), SUM(e.salary)
FROM department AS d
JOIN employee AS e ON d.dpt_no = e.dpt_no
GROUP BY d.name