select 部門名稱,salary.月份,max(sum(salary.工資)) 最高工資,min(sum(salary.工資)) 最低工資
from Employee,Departments,Salary
where Employee.員工ID = Salary.員工ID
and Employee.部門ID = Departments.部門ID
group by 部門名稱 ,salary.月份
如果需要限定 月份，則為：
create view Dep_ MSalary as
select 部門名稱,max(sum(salary.工資)) 最高工資,min(sum(salary.工資)) 最低工資
from Employee,Departments,Salary
where Employee.員工ID = Salary.員工ID
and Employee.部門ID = Departments.部門ID
and salary.月份 = xxx
group by 部門名稱