text: USE employee_tracker;
  
  SET FOREIGN_KEY_CHECKS=0;
  DROP TABLE IF EXISTS manager;
  DROP TABLE IF EXISTS employee;
  DROP TABLE IF EXISTS role;
  DROP TABLE IF EXISTS department;
  SET FOREIGN_KEY_CHECKS=1;
  
  CREATE TABLE department (
      id INTEGER AUTO_INCREMENT PRIMARY KEY,
      department_name VARCHAR(30) NOT NULL
  );
  
  CREATE TABLE role (
      id INTEGER AUTO_INCREMENT PRIMARY KEY,
      title VARCHAR(30) NOT NULL,
      salary DECIMAL,
      department_id INT,
      FOREIGN KEY (department_id) REFERENCES department(id)
  );
  
  CREATE TABLE manager (
      id INTEGER AUTO_INCREMENT PRIMARY KEY,
      boss_first_name VARCHAR(30) NOT NULL,
      boss_last_name VARCHAR(30) NOT NULL,
      role_id INT,
      FOREIGN KEY (role_id) REFERENCES role(id)
  );
  
  CREATE TABLE employee (
      id INTEGER AUTO_INCREMENT PRIMARY KEY,
      first_name VARCHAR(30) NOT NULL,
      last_name VARCHAR(30) NOT NULL,
      role_id INT,
      manager_id INT,
      FOREIGN KEY (role_id) REFERENCES role(id),
      FOREIGN KEY (manager_id) REFERENCES manager(id)
  );