sql server 使用计算列

Question

我有一个这样的查询:

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

我如何使用计算列total_price来计算其他这样的总计？

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

这可能吗？

Answer 1

不，不可能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

Things happen "all at once" in SQL, not "from left to right" as they would in a sequential file/procedural language model

您可以在 CTE 中定义它，然后在 CTE 之外重新使用它。

示例

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