Exercise 5：579.Find Cumulative Salary Of An Employee Problem

1.Description

The Employee table holds the salary information in a year.

Write a SQL to get the cumulative sum of an employee’s salary over a period of 3 months but exclude the most recent month.

The result should be displayed by ‘Id’ ascending, and then by ‘Month’ descending.

Example Input

| Id | Month | Salary |
|----|-------|--------|
| 1  | 1     | 20     |
| 2  | 1     | 20     |
| 1  | 2     | 30     |
| 2  | 2     | 30     |
| 3  | 2     | 40     |
| 1  | 3     | 40     |
| 3  | 3     | 60     |
| 1  | 4     | 60     |
| 3  | 4     | 70     |

Output

| Id | Month | Salary |
|----|-------|--------|
| 1  | 3     | 90     |
| 1  | 2     | 50     |
| 1  | 1     | 20     |
| 2  | 1     | 20     |
| 3  | 3     | 100    |
| 3  | 2     | 40     |

Explanation:Employee ‘1’ has 3 salary records for the following 3 months except the most recent month ‘4’: salary 40 for month ‘3’, 30 for month ‘2’ and 20 for month ‘1’ So the cumulative sum of salary of this employee over 3 months is 90(40+30+20), 50(30+20) and 20 respectively.

| Id | Month | Salary |
|----|-------|--------|
| 1  | 3     | 90     |
| 1  | 2     | 50     |
| 1  | 1     | 20     |

Employee ‘2’ only has one salary record (month ‘1’) except its most recent month ‘2’.

| Id | Month | Salary |
|----|-------|--------|
| 2  | 1     | 20     |

Employ ‘3’ has two salary records except its most recent pay month ‘4’: month ‘3’ with 60 and month ‘2’ with 40. So the cumulative salary is as following.

| Id | Month | Salary |
|----|-------|--------|
| 3  | 3     | 100    |
| 3  | 2     | 40     |

2.Create Table and insert into values

create table if not exists leetcode.ex_579_employee
(
 id int, 
 month int,
 salary int
)  stored as orc ;

INSERT INTO table leetcode.ex_579_employee  VALUES
('1' , '1' ,'20'),
('2' , '1' ,'20'),
('1' , '2' ,'30'),
('2' , '2' ,'30' ),
('3' , '2' ,'40' ),
('1' , '3' ,'40' ),
('3' , '3' ,'60' ),
('1' , '4' ,'60' ),
('3' , '3' ,'70' )