MySQL的平均值和總數

Question

這是我的代碼，但所有值都相同。

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

Answer 1

你缺少的表之間的連接狀態，所以你把它們合併爲一個完整的交叉產品，而不是員工只鏈接到他們的部門。

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