Same Department Same Salary Pairs

Return pairs of employees in the same department earning exactly the same salary, smaller id first.

Table schema

Employees(id INT PRIMARY KEY, name VARCHAR(10), dept VARCHAR(10), salary INT)

Sample data

id | name | dept | salary
1 | Ann | IT | 50
2 | Bob | IT | 50
3 | Cy | IT | 60
4 | Dee | HR | 50
5 | Eli | HR | 50
6 | Fay | HR | 70