text: INSERT INTO department (name)
  VALUES ("Front-end"),
         ("Back-end"),
         ("Tester"),
         ("UX");
  
  INSERT INTO role (title, salary, department_id)
  VALUES ("Front-end developer", 32321.00, 1),
         ("Back-end developer", 38000.00, 2),
         ("Unit tester", 26000.00, 3),
         ("End-to-end tester", 46000.00, 3),
         ("UX design", 32000.00, 4),
         ("Manager", 75000, 4);
   
  INSERT INTO employee (first_name, last_name, role_id, manager_id)
  VALUES ("Joe", "Bloggs", 1, NULL),
         ("Jane", "Doe", 2, 1),
         ("John", "Smith", 2, 1),
         ("Joe", "Bloggs", 3, 3);
  