CREATE TABLE Employees (
    id INT PRIMARY KEY,
    name VARCHAR(50),
    salary DECIMAL(10, 2),
    manager_id INT
);

INSERT INTO Employees (id, name, salary, manager_id) VALUES
(1, 'Employee1', 5000, NULL),
(2, 'Employee2', 6000, 1),
(3, 'Employee3', 7000, 1),
(4, 'Employee4', 8000, 2),
(5, 'Employee5', 9000, 2),
(6, 'Employee6', 4000, 3);