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 |
+------------+----------+--------+
思路1:通過連表,判斷相應的最高工資
select d.name as Department,e.name as Employee,e.Salary
from Department as d,Employee as e
where d.Id=e.DepartmentId and e.Salary=(Select max(Salary) from Employee where DepartmentId=d.Id)
思路2:通過group by 把每個部門的最高工資查出來,再通過連表
SELECT
d.`Name` AS Department ,
e.`Name` AS Employee ,
e.Salary
FROM (SELECT departmentId,max(Salary) AS Salary FROM employee GROUP BY DepartmentId) AS x,
employee AS e,department AS d
WHERE x.departmentId=e.DepartmentId and x.Salary=e.Salary and e.DepartmentId=d.Id