mysql - MySQL乘法浮点数列:1 * 7.6给出7.599999904632568？

当我查询SELECT 1*7.6时，它会让我感到7.6
但当我进行列乘法运算时（products.commission*salled.amount）：

SELECT *,
(products.commision*sold.amount) as fee
FROM sold
RIGHT JOIN products
ON sold.idprod=products.ID
AND DATE(sold.date) BETWEEN DATE('2015-10-01') AND DATE('2015-10-31')
WHERE sold.userid="1"
ORDER BY sold.userid

我很高兴

ID | userid | date     | idprod | amount | Category | Name  | commision  | fee
60 | 1      | 15-10-01 | 21     | 1      | Volish   | Black | 7.6(float) | 7.599999904632568

为什么？

最佳答案

在进行比较时，必须将值类型转换为整数/小数，而不是浮点

(CAST(products.commision AS Decimal(7,2)) * CAST(sold.amount AS Decimal(7,2))) as fee

从https://dev.mysql.com/doc/refman/5.0/en/cast-functions.html和casting a floating to decimal in mysql
十进制将值设为十进制，用7位表示最大大小和2位数的最大精度（12345.67）。
编辑：我不确定将CAST添加到原始值还是简单地将答案转换为

(products.commision  * sold.amount ) as CAST(fee AS Decimal(7,2))