Php Mysql-按两个价格列作为一列订购

我有这样一个产品表：

   id  | name     | price |discount| discount_price
    1  | Product 1| 100   | 0      |
    2  | Product 2| 150   | 1      | 75
    3  | Product 3| 200   | 1      | 80

我想做一个按价格递增的过滤器。但是当我想按价格排序时，我只能做一列

没有折扣价格列，就没有正确的订单

我需要得到这样的结果（价格上涨）：

这就行了

select
    id,
    name,
    price,
    discount,
    discount_price
from
    table
order by
    (case
        when discount_price = '' then  CAST(price as INT)
        else CAST(discount_price as INT)
    end);

看见

select
    id,
    name,
    price,
    discount,
    discount_price
from
    table
order by
    (case
        when discount_price = '' then  CAST(price as INT)
        else CAST(discount_price as INT)
    end);