是否可以使用两行的输出来计算第三行

Question

SELECT .......

---a long calculation-- AS MARGIN,

---calculation--- AS SALES

FROM          .....
where .....
GROUP BY .....
order by REV desc;

现在我想添加另一列为“保证金百分比”，即 保证金/销售。 我该如何做而不重新计算MARGIN和SALES？ 所以输出表将是：

| Margin | SALES | Margin percent

Answer 1

以derived table（即子查询）结束当前查询。对结果进行百分比计算。

select margin, sales, margin * 100.0 /sales
from
(   
    SELECT .......

    ---a long calculation-- AS MARGIN,

    ---calculation--- AS SALES

    FROM          .....
    where .....
    GROUP BY .....
) dt