sql-server-2008 - 为什么SQL中的数学运算返回0

Question

为什么CALC下面的 TSQL 查询中没有计算出值？

SELECT
    D1, D2, (D1+D2) As 'Sum', ((D1/(D1+D2))*100) As CALC
FROM
    (SELECT 3 As D1, 6 As D2) A

这是我得到的结果：

D1          D2          Sum         CALC
----------- ----------- ----------- -----------
3           6           9           0

Answer 1

整数除以整数生成整数，因此如果操作数都是整数，则除法运算将截断结果的小数部分。将一个更改为浮点数或小数以修复它。

跑去 Select 5 / 6, 5 / 6.0看看我的意思

使用演员表修复您的代码...

 SELECT  D1, D2, (D1+D2) As 'Sum', 
    ((D1/ Cast(D1+D2 as Float))*100) As CALC
 FROM (SELECT 3 As D1, 6 As D2) A

或者只是使值浮动以开始：

 SELECT  D1, D2, (D1+D2) As 'Sum', 
    ((D1/ (D1+D2))*100) As CALC
 FROM (SELECT 3.0 As D1, 6.0 As D2) A

Answer 2

整数除法四舍五入到零
移动 100。你仍然会得到一些四舍五入。
如果您不能容忍任何舍入，则不要使用整数。

SELECT
    D1, D2, (D1+D2) As 'Sum', D1/(D1+D2) as frac, (D1*100)/(D1+D2) As pct
FROM
    (SELECT 3 As D1, 6 As D2) A