[SQL]LeetCode185. 部門工資前三高的員工 | Department Top Three Salaries

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SQL 架構

 1 Create table If Not Exists Employee (Id int, Name varchar(255), Salary int, DepartmentId int)
 2 Create table If Not Exists Department (Id int, Name varchar(255))
 3 Truncate table Employee
 4 insert into Employee (Id, Name, Salary, DepartmentId) values ('1', 'Joe', '70000', '1')
 5 insert into Employee (Id, Name, Salary, DepartmentId) values ('2', 'Henry', '80000', '2')
 6 insert into Employee (Id, Name, Salary, DepartmentId) values ('3', 'Sam', '60000', '2')
 7 insert into Employee (Id, Name, Salary, DepartmentId) values ('4', 'Max', '90000', '1')
 8 Truncate table Department
 9 insert into Department (Id, Name) values ('1', 'IT')
10 insert into Department (Id, Name) values ('2', 'Sales')

---

The Employee table holds all employees. Every employee has an Id, and there is also a column for the department Id.

+----+-------+--------+--------------+
| Id | Name  | Salary | DepartmentId |
+----+-------+--------+--------------+
| 1  | Joe   | 70000  | 1            |
| 2  | Henry | 80000  | 2            |
| 3  | Sam   | 60000  | 2            |
| 4  | Max   | 90000  | 1            |
| 5  | Janet | 69000  | 1            |
| 6  | Randy | 85000  | 1            |
+----+-------+--------+--------------+

The Department table holds all departments of the company.

+----+----------+
| Id | Name     |
+----+----------+
| 1  | IT       |
| 2  | Sales    |
+----+----------+

Write a SQL query to find employees who earn the top three salaries in each of the department. For the above tables, your SQL query should return the following rows.

+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT         | Max      | 90000  |
| IT         | Randy    | 85000  |
| IT         | Joe      | 70000  |
| Sales      | Henry    | 80000  |
| Sales      | Sam      | 60000  |
+------------+----------+--------+

---

Employee 表包含全部員工信息，每一個員工有其對應的 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            |
| 5  | Janet | 69000  | 1            |
| 6  | Randy | 85000  | 1            |
+----+-------+--------+--------------+

Department 表包含公司全部部門的信息。

+----+----------+
| Id | Name     |
+----+----------+
| 1  | IT       |
| 2  | Sales    |
+----+----------+

編寫一個 SQL 查詢，找出每一個部門工資前三高的員工。例如，根據上述給定的表格，查詢結果應返回：

+------------+----------+--------+
| Department | Employee | Salary |
+------------+----------+--------+
| IT         | Max      | 90000  |
| IT         | Randy    | 85000  |
| IT         | Joe      | 70000  |
| Sales      | Henry    | 80000  |
| Sales      | Sam      | 60000  |
+------------+----------+--------+

---

302ms

 1 # Write your MySQL query statement below
 2 
 3 SELECT D.Name AS Department,E.Name as Employee,Salary
 4 FROM (
 5 SELECT IF(@pre=DepartmentId,IF(@pre_salary<=>@pre_salary:=Salary,@rank,@rank:=@rank+1),@rank:=1) AS Rank,
 6     Name,Salary,@pre:=DepartmentId AS DepartmentId
 7 FROM Employee,(SELECT @pre:=0,@rank:=0,@pre_salary:=NULL) v
 8 ORDER BY DepartmentId,Salary DESC
 9 ) E
10 INNER JOIN Department D
11 ON E.DepartmentId=D.Id
12 WHERE Rank<=3

---

309ms

1 select d.Name as Department, e.Name as Employee, Salary
2 from Employee e join Department d on e.DepartmentId = d.Id
3 where 3 >= (
4     select count(*)
5     from (select distinct DepartmentId as dept_id, Salary from Employee) as e1
6     where e1.dept_id = e.DepartmentId and e1.salary >= e.salary
7 )
8 order by Department, e.Salary desc

---

323ms

 1 # Write your MySQL query statement below
 2 
 3 # 99.7%
 4 select d.Name Department, e.Name Employee, e.Salary
 5 from (  select @rn := case when @dept = DepartmentId and @sal =  Salary then @rn 
 6                            when @dept = DepartmentId and @sal <> Salary then @rn + 1
 7                            else 1 end  rows,
 8                @dept := DepartmentId, @sal := Salary, employee.*
 9         from employee, (select @rn := 0, @dept := 0, @sal:= -1) t
10         order by DepartmentId, Salary desc) e,
11       Department d
12 where d.Id = e.DepartmentId
13 and e.rows <= 3
14 order by Department, Salary desc;

---

325ms

 1 # Write your MySQL query statement below
 2 select Name as Department, Employee, Salary
 3 from (
 4         select Name as Employee, Salary, DepartmentId as Id,
 5             @rank := if(@id = (@id := DepartmentId), @rank, 0)
 6                 + (@salary <> (@salary := Salary)) as Rank
 7         from Employee, (select @rank := 0, @id := -1, @salary := -1) init
 8         order by DepartmentId, Salary desc
 9     ) as rankek join Department using (Id)
10 where Rank <= 3