FOR x IN ( SELECT COUNT(*) cnt
            FROM DUAL
           WHERE EXISTS ( SELECT NULL FROM task
                           WHERE task.task_type_id = lib.task_type_check()
                             AND task.task_status_id = lib.task_status_open()
                             AND task.unit_id = in_unit_id
                             AND task.station_id = v_station_id
                        )
         )
LOOP
  IF( x.cnt = 1 ) THEN
    v_task_exist := TRUE;
  ELSE
    v_task_exist := FALSE;
  END IF;
END LOOP;