Calculate the difference between the sum of the highest salaries and the sum of the lowest salaries in the company. The table "playground.employees_salary" contains columns "id" (unique employee ID), "name" (employee's name), and "salary" (employee's salary as a positive integer). The result should be a single column "difference" with one row representing the calculated difference. If the "playground.employees_salary" table is empty, "difference" should be 0.

• id int
• name string
• salary int

SELECT * FROM playground.employees_salary LIMIT 100