LeetCode：Department Highest Salary - 部门内最高工资
1、题目名称
Department Highest Salary（部门内最高工资）
2、题目地址
https://leetcode.com/problems/department-highest-salary/
3、题目内容
表Employee包括四列：Id、Name、Salary、DepartmentId
+----+-------+--------+--------------+ | Id | Name | Salary | DepartmentId | +----+-------+--------+--------------+ | 1 | Joe | 70000 | 1 | | 2 | Henry | 80000 | 2 | | 3 | Sam | 60000 | 2 | | 4 | Max | 90000 | 1 | +----+-------+--------+--------------+
表Department表中包括了公司的所有部门
+----+----------+ | Id | Name | +----+----------+ | 1 | IT | | 2 | Sales | +----+----------+
现要求写一个SQL，求出某一部门内领取最高工资的员工。
+------------+----------+--------+ | Department | Employee | Salary | +------------+----------+--------+ | IT | Max | 90000 | | Sales | Henry | 80000 | +------------+----------+--------+
4、初始化数据库脚本
在MySQL数据库中建立一个名为LEETCODE的数据库，用MySQL命令行中的source命令执行下面脚本：
-- 执行脚本前必须建立名为LEETCODE的DATABASE USE LEETCODE; DROP TABLE IF EXISTS Employee; CREATE TABLE Employee ( Id INT NOT NULL PRIMARY KEY, Name VARCHAR(50), Salary INT, DepartmentId INT ); INSERT INTO Employee (Id, Name, Salary, DepartmentId) VALUES (1, 'Joe', 70000, 1); INSERT INTO Employee (Id, Name, Salary, DepartmentId) VALUES (2, 'Henry', 80000, 2); INSERT INTO Employee (Id, Name, Salary, DepartmentId) VALUES (3, 'Sam', 60000, 2); INSERT INTO Employee (Id, Name, Salary, DepartmentId) VALUES (4, 'Max', 90000, 1); DROP TABLE IF EXISTS Department; CREATE TABLE Department ( Id INT NOT NULL PRIMARY KEY, Name VARCHAR(50) ); INSERT INTO Department (Id, Name) VALUES (1, 'IT'); INSERT INTO Department (Id, Name) VALUES (2, 'Sales');
5、解题SQL1
一个思路是，先求出各个部门的最高工资，再考察Employee表中，工资数等于所在部门的最高工资的员工，即为所求。
SELECT D.Name AS Department, E.Name AS Employee, MAXS_D.MAXS AS Salary FROM Employee AS E, Department AS D, ( SELECT MAX(Salary) AS MAXS, DepartmentId FROM Employee GROUP BY DepartmentId) AS MAXS_D WHERE E.Salary = MAXS_D.MAXS AND E.DepartmentId = D.Id AND E.DepartmentId = MAXS_D.DepartmentId;
6、解题SQL2
另一个思路是，在同一部门中，工资大于等于该部门所有员工的员工，即为所求。
SELECT D.Name AS Department, E.Name AS Employee, E.Salary AS Salary FROM Employee AS E, Department AS D WHERE E.DepartmentId = D.Id AND Salary >= ALL( SELECT Salary FROM Employee E_TMP WHERE E_TMP.DepartmentId = E.DepartmentId);
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