CREATE DEFINER=`root`@`localhost` PROCEDURE `curdemo`()
BEGIN

  DECLARE done INT DEFAULT 0;

  DECLARE userid,repid  INT;

  DECLARE cur1 CURSOR FOR select u.userid,u.repid from user u,personalwebsite p where
  p.url <> u.repid and p.distributorid = u.userid
  and p.url = u.userid;

  DECLARE CONTINUE HANDLER FOR SQLSTATE '02000' SET done = 1;
 
  OPEN cur1;

 
  REPEAT

    FETCH cur1 INTO userid,repid;
 
    IF NOT done THEN

       update personalwebsite set url = repid where distributorid = userid;

    END IF;

  UNTIL done END REPEAT;

  CLOSE cur1;

END;

参考：http://dev.mysql.com/doc/refman/5.1/zh/stored-procedures.html#declare-cursors