/*注意题目是部门和薪资降序排序含义,是先按薪资在部门内排序，再主查询按部门排序*/
select t.department
,t.employee_name
,t.salary
from(
select department
,employee_name
,salary
,row_number() over(partition by department order by salary desc) as rk 
from employees
) t
where rk <= 2