text: --CREATE DML-TRIGGER not_create_new_room WHICH PROHIBIT INSERTION OF NEW RECORDS TO TABLE Rooms
  CREATE OR REPLACE TRIGGER not_create_new_room
  BEFORE INSERT ON ROOMS FOR EACH ROW
  
  DECLARE
    roomsCount NUMBER;
  
  BEGIN
    SELECT COUNT(*) INTO roomsCount FROM ROOMS;
    
    IF roomsCount >= 12 THEN
      raise_application_error(-20001, 'Добавить новый номер невозможно');
    END IF;
  END;
  
  