Mysql案例5：取得平均薪资最高的部门的部门名称

SELECT 
            e.departmentid,d.name,AVG(e.salary) avgsal
FROM 
            employee e
INNER JOIN
            department d
ON
            e.departmentid =d.id

GROUP BY 
            e.departmentid,d.`name`
HAVING 
            avgsal = (
                                SELECT 
                                            MAX(t.avgsal) maxsal
                                FROM (
                                            SELECT departmentid,AVG(salary) avgsal
                                            FROM employee
                                            GROUP BY departmentid) t
                                )