为什么SQL中的数学运算返回0

Question

为什么CALC值未在下面的TSQL查询中计算？

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

整数除以整数会生成一个整数，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十进制数来修复它。

运行Select 5 / 6, 5 / 6.0以查看我的意思

使用强制转换修复代码...

 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

或者只是让值浮动开始于：

 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

整数除法四舍五入为零 移动100.你仍然会得到一些四舍五入 如果你不能容忍任何舍入，那么不要使用整数。

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