Employee 表包含所有員工信息,每個員工有其對應的 Id, salary 和 department Id。
+----+-------+--------+--------------+
| Id | Name | Salary | DepartmentId |
+----+-------+--------+--------------+
| 1 | Joe | 70000 | 1 |
| 2 | Henry | 80000 | 2 |
| 3 | Sam | 60000 | 2 |
| 4 | Max | 90000 | 1 |
+----+-------+--------+--------------+
Department 表包含公司所有部門的信息。
+----+----------+
| Id | Name |
+----+----------+
| 1 | IT |
| 2 | Sales |
+----+----------+
編寫一個 SQL 查詢,找出每個部門工資最高的員工。例如,根據上述給定的表格,Max 在 IT 部門有最高工資,Henry 在 Sales 部門有最高工資。
+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT | Max | 90000 |
| Sales | Henry | 80000 |
+------------+----------+--------+
來源:力扣(LeetCode)
鏈接:https://leetcode-cn.com/problems/department-highest-salary
注意: 同一個部門最高工資可能有多個人
排序函數:
ROW_NUMBER OVER(partition by … order by … desc):無並列,相同名次順序排列
RANK OVER(partition by … order by … desc):有並列,跳躍排序,有兩個第二名時後邊跟着的是第四名
DENSE_RANK OVER(partition by … order by … desc):有並列,連續排序,有兩個第二名時仍然跟着第三名
這題用rank() 和 dense_rank() 的結果一樣。
select Department, Employee, Salary
from
(select e.Name Employee, e.Salary Salary, d.Name Department,
dense_rank() over(partition by e.DepartmentId order by Salary desc) ranking
from Employee e
join Department d
on e.DepartmentId = d.Id) t
where ranking =1;