Assign Row Numbers to Employees Table

Question

Assign a row number to employees ordered by salary within each department.

Accepted Answer

```sql
SELECT 
    id, 
    name, 
    department_id, 
    salary, 
    ROW_NUMBER() OVER (PARTITION BY department_id ORDER BY salary DESC) AS row_num
FROM employees;
```

This query uses the `ROW_NUMBER()` window function to assign a unique sequential integer to each employee within their respective `department_id` partition, ordered by `salary` in descending order.