drop procedure if exists  P_SEQUENCE;

/** 暂省略包
  @AUTO LIANGRUI 2014/6/27
  T_PRO_PRODUCT 表
	排序 对整个表进行按序号排序 
  根据序号从新自然排序 重复序号的安创建日期分配序号
	测试阶段

  测试调用
	set @merid='TEST66';
	call P_SEQUENCE(@merid);
	**/
create procedure P_PRODUCT_SEQUENCE( in v_merchar_id VARCHAR(100)) 
begin

  DECLARE v_id    VARCHAR(100);
  DECLARE v_rowNo VARCHAR(100);
  DECLARE flag int;
  DECLARE e_error INTEGER DEFAULT 0;  


  -- 定义游标
 DECLARE c_cur CURSOR  for 
   Select a.id ,(@rowNum:=@rowNum+1) as rowNo
    From T_PRO_PRODUCT a ,(Select (@rowNum :=0)) b 
     where MERCHANT_ID=v_merchar_id
      order by ISNULL(a.sequence),a.sequence,a.create_dt;

   DECLARE CONTINUE HANDLER FOR NOT FOUND SET flag=1; 
   DECLARE CONTINUE HANDLER FOR SQLEXCEPTION SET e_error=1; 
   SET flag=0; 

   OPEN c_cur;
    -- 循环所有的行
   REPEAT
      FETCH c_cur INTO v_id,v_rowNo;     
    update T_PRO_PRODUCT SET sequence= v_rowNo where ID=v_id;
       -- 循环结束
      UNTIL flag
   END REPEAT;

   -- 关闭游标
   CLOSE  c_cur;

	-- 事务处理
	IF e_error = 1 THEN
			ROLLBACK;
	ELSE
			COMMIT;
	END IF;

end

上面的其实可以进行简化

SET @colNo = 0;
UPDATE T_PRO_PRODUCT SET SEQUENCE=(@colNo:=@colNo+1) WHERE MERCHANT_ID='TEST66' ORDER BY SEQUENCE, CREATE_DT DESC;