sql练习:部门工资最高的员工
题目:
表: Employee
+--------------+---------+ | 列名 | 类型 | +--------------+---------+ | id | int | | name | varchar | | salary | int | | departmentId | int | +--------------+---------+ 在 SQL 中,id是此表的主键。 departmentId 是 Department 表中 id 的外键(在 Pandas 中称为 join key)。 此表的每一行都表示员工的 id、姓名和工资。它还包含他们所在部门的 id。
表: Department
+-------------+---------+ | 列名 | 类型 | +-------------+---------+ | id | int | | name | varchar | +-------------+---------+ 在 SQL 中,id 是此表的主键列。 此表的每一行都表示一个部门的 id 及其名称。
查找出每个部门中薪资最高的员工。
按 任意顺序 返回结果表。
查询结果格式如下例所示。
示例 1:
输入: Employee 表: +----+-------+--------+--------------+ | id | name | salary | departmentId | +----+-------+--------+--------------+ | 1 | Joe | 70000 | 1 | | 2 | Jim | 90000 | 1 | | 3 | Henry | 80000 | 2 | | 4 | Sam | 60000 | 2 | | 5 | Max | 90000 | 1 | +----+-------+--------+--------------+ Department 表: +----+-------+ | id | name | +----+-------+ | 1 | IT | | 2 | Sales | +----+-------+ 输出: +------------+----------+--------+ | Department | Employee | Salary | +------------+----------+--------+ | IT | Jim | 90000 | | Sales | Henry | 80000 | | IT | Max | 90000 | +------------+----------+--------+ 解释:Max 和 Jim 在 IT 部门的工资都是最高的,Henry 在销售部的工资最高。
解答:
l 写法一:
select Department.name as Department , Employee.name as Employee , Employee.salary as Salary
from Employee JOIN Department ON Employee.departmentId= Department.Id
where (Employee.departmentId ,Salary) IN
(select departmentId ,MAX(salary)
from Employee
group by departmentId);
l 写法二:
SELECT
Department.NAME AS Department,
Employee.NAME AS Employee,
Salary
FROM
Employee,
Department
WHERE
Employee.DepartmentId = Department.Id
AND ( Employee.DepartmentId, Salary )
IN (SELECT DepartmentId, max( Salary )
FROM Employee
GROUP BY DepartmentId )