sql server使用计算列

Question

我有这样的查询：

select 
(price1 + price2 + price3) as total_price 
from prices

如何使用计算列total_price来计算其他总数？<​​/ p>

select 
(price1 + price2 + price3) as total_price,
(price4 + total_price) as total_price2
from prices    

这可能吗？

Answer 1

否则无法引用在同一级别定义的列别名。出现在同一逻辑查询处理阶段的表达式为evaluated as if at the same point in time。

As Joe Celko says

  

事情在SQL中“一下子”发生，而不是“从左到右”   将在顺序文件/程序语言模型

您可以在CTE中定义它，然后在CTE外重复使用它。

实施例

WITH T
     AS (SELECT ( price1 + price2 + price3 ) AS total_price,
                price4
         FROM   prices)
SELECT total_price,
       ( price4 + total_price ) AS total_price2
FROM   T  

Answer 2

如果经常使用

，我还会在桌面上考虑computed column

ALTER  TABLE prices ADD
   total_price AS (price1 + price2 + price3)

然后您的查询

select 
    total_price,
    (price4 + total_price) as total_price2
from prices

这样，您可以应用DRY原则......

Answer 3

select T.total_price,
       P.price4 + T.total_price as total_price2
from prices as P
  cross apply (select P.price1 + P.price2 + P.price3) as T(total_price)