What is the difference in salary of the top 2 employees with the highest number of territories in charge?
highest number of territories refers to max(TerritoryID); difference in salary = subtract(employeeA.Salary, employeeB.Salary)
SELECT MAX(Salary) - MIN(Salary) FROM ( SELECT T1.Salary FROM Employees AS T1 INNER JOIN EmployeeTerritories AS T2 ON T1.EmployeeID = T2.EmployeeID GROUP BY T1.EmployeeID, T1.Salary ORDER BY COUNT(T2.TerritoryID) DESC LIMIT 2 ) T1