Calculate Employee Salary Percentage by Department

Question

Find the percentage contribution of each employee's salary to the total department salary.

Accepted Answer

```sql
SELECT 
    name, 
    salary, 
    (salary / SUM(salary) OVER (PARTITION BY department_id)) * 100 AS percentage_contribution
FROM employees;
```

This query calculates the percentage of each employee's salary relative to the total salary of their respective department using the `SUM()` window function partitioned by `department_id`.