将sql中两列之间的值相乘

我的问题

SELECT  DATEDIFF(day,SD.STARTDATE,SD.ENDDATE) AS TotalDays ,amount 
FROM staydetails 

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例如，金额列的值可能为

100

，我需要将

totaldays

和

amount

的值相乘，然后将结果添加到另一列。

只需将计算列添加到选择列表中，如下所示：

 select  
 DATEDIFF(day,SD.STARTDATE,SD.ENDDATE) AS TotalDays ,
 amount,
 (DATEDIFF(day,SD.STARTDATE,SD.ENDDATE) * amount) AS CalculatedAmount
from staydetails

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请注意，您需要重复

DATEDIFF

功能-您不能使用别名TotalDays。

非常简单：

select  DATEDIFF(day,SD.STARTDATE,SD.ENDDATE) AS TotalDays ,amount,
        (DATEDIFF(day,SD.STARTDATE,SD.ENDDATE) * amount) as Result 
from staydetails 

---

就这样乘以它们：

select  DATEDIFF(day,SD.STARTDATE,SD.ENDDATE) AS TotalDays ,
        amount ,
        DATEDIFF(day,SD.STARTDATE,SD.ENDDATE) * amount AS CalculatedValue
from staydetails

您可能试图引用

TotalDays

如下：

TotalDays*amount

，但您必须对基础值执行计算，该值是

DATEDIFF

计算的结果，而不是别名列名