LeetCode: Find Cumulative Salary of an Employee

Find Cumulative Salary of an Employee

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• Tag: #sql

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     |

Github: code.dennyzhang.com

Credits To: leetcode.com

Leave me comments, if you have better ways to solve.

## https://code.dennyzhang.com/find-cumulative-salary-of-an-employee