CREATE PROCEDURE addCity6()
BEGIN

    DECLARE done INT DEFAULT FALSE;
    DECLARE S_START CHAR(20);
    DECLARE S_END CHAR(20);
    DECLARE PRICE INT;

    DECLARE CUR CURSOR FOR SELECT start,price,end 
              FROM truck 
                 WHERE id NOT IN (
                          select a.id from truck a, truck b where a.start=b.end and a.end = b.start);
  DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1;

  OPEN CUR;
  REPEAT
    FETCH CUR INTO S_START,PRICE,S_END;
  IF NOT done THEN
        INSERT INTO truck(start,price,end)VALUES(S_END,PRICE,S_START);
        COMMIT;
  END IF;
 UNTIL done END REPEAT;
 CLOSE CUR;
END;