LeetCode--184.部门最高工资

建表

Create table If Not Exists Employee (Idint, Name varchar(255), Salary int, DepartmentId int);
Create table If Not Exists Department (Idint, Name varchar(255));
Truncate table Employee;
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');
Truncate table Department;
insert into Department (Id, Name) values('1', 'IT');
insert into Department (Id, Name) values('2', 'Sales');

子查询把每个部门的最高工资找到，然后作为表联查的条件

select d.`Name`, e.`Name`, e.Salary
 from Employee e, Department d, 
  (select DepartmentId,max(Salary) 最高工资 from Employee GROUP BY DepartmentId) tmp
 where e.DepartmentId = d.Id
 and e.Salary = tmp.最高工资
 ORDER BY e.Salary desc

另一种思路

select d.Name as Department,e1.Name as Employee,e1.Salary as Salary
from Employee e1 , Department d
where e1.DepartmentId=d.Id  and (e1.Salary,e1.DepartmentId) 
in (select max(Salary),DepartmentId from Employee group by DepartmentId)