Mysql-group先分組后排序

1、先分組后排序、考慮並列第一

 

#錯誤寫法
SELECT
    b.depName AS departId,
    a.`name` AS employee,
    max(salary) AS salary
FROM
    cs_employee a
LEFT JOIN cs_depart b ON a.departId = b.id
GROUP BY
    a.departId


#正確寫法（先取出部門不為空的工資最大值，然后關聯查詢）
SELECT
    a.max AS salary,
    b.`name` AS employee,
    c.depName AS departId
FROM
    (SELECT MAX(salary) max FROM cs_employee t WHERE t.departId is NOT NULL GROUP BY t.departId ) a 
LEFT JOIN cs_employee b ON  a.max = b.salary
LEFT JOIN cs_depart c ON b.departId = c.id
ORDER BY b.departId