LC 185部门工资前三高的所有员工Department Top Three Salaries　困难

Employee 表含员工工资与部门 id，Department 表存部门名；找出每个部门工资前三高的员工，输出部门名、员工名、工资。

思路 窗口函数 DENSE_RANK 按部门对工资降序排名，取 rk <= 3。

SELECT D.name AS Department,
       E.name AS Employee,
       E.salary AS Salary
FROM (
  SELECT name, salary, departmentId,
         DENSE_RANK() OVER (
           PARTITION BY departmentId
           ORDER BY salary DESC) AS rk
  FROM Employee
) E
JOIN Department D ON E.departmentId = D.id
WHERE E.rk <= 3;

数据表：Employee,Department　·　关键字：找出每个部门工资前三高的员工，输出部门名、员工名、工资