添加浮点数不会产生正确的结果 [英] Adding floats does not yield a correct result

问题描述

想象一下以下情况。
循环中将金额加到总计中：

Imagine the following situation. Amounts are added to a total in a loop:

float total = 0;
float[] amounts = new float[]{...};
foreach(float amount in amounts)
{
  total += amount;
}

总计，为因为所有金额都已写入数据库。
当我在SQL中计算 SUM（amount）时，它得出的值不同于总计。
而且，当我在C＃中执行相同的计算时，但是这次将金额加到类型double的值上，

total, as wel as all the amounts are written to a database. When I calculate SUM(amount) in SQL, it results in a value that differs from total. Moreover, when I do the same calculation in C#, but this time adding the amounts to a value of type double,

double total = 0;
//the rest of the code is the same as above

然后是 total 代表正确的值。

这可能是由浮点数和双精度数之间的精度差异引起的吗？

Could this be caused by the difference in precision between a float and a double?

请注意，这取决于值。此计算的大多数结果 是正确的。

Note that it depends on the values. Most of the results of this calculation are correct.

推荐答案

是。 SQL Server的浮点大小是不同的，但数据库中可能有8个字节的浮点。当您在C＃代码中使用double（8字节）时，结果是相同的，而当使用float（4字节）时，结果却不同。浮点值范围内的double值将与浮点值不同。

Yes. SQL Server's float size is variant but you likely have 8 byte floats in the database. When you use doubles ( 8 bytes ) in the C# code the results are the same, when you use floats ( 4 bytes ) they're different. double values within the range of a float will not be the same as the float values.

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