185. 部门工资前三高的所有员工 + 多表联合 + join + dense_rank()

185. 部门工资前三高的所有员工

LeetCode_MySql_185

题目描述

方法一：使用join on

# Write your MySQL query statement below
select d.Name as 'Department', e1.Name as 'Employee', Salary
from Employee e1 join Department d on e1.DepartmentId = d.Id
where
    3 >( # 查找工资高于e1.Salary的个数
        select count(distinct Salary)
        from Employee e2
        where e1.DepartmentId = e2.DepartmentId
            and e1.Salary < e2.Salary
    );

方法二：使用dense_rank() over

# Write your MySQL query statement below
/**
解题思路:先对Employee表进行部门分组工资排名，再关联Department表查询部门名称，再使用WHERE筛选出排名小于等于3的数据（也就是每个部门排名前3的工资）。
**/
select b.Name as Department, e2.Name as Employee, e2.Salary
from
    Department b join
    (
        select DepartmentId, Name, Salary, dense_rank() over(partition by DepartmentId order by Salary desc) as rankId
        from Employee
    ) as e2
    on e2.DepartmentId = b.Id
where e2.rankId <= 3;