浮点数和十进制数据类型的区别

2021-11-20 00:00:00 mysql

在 MySQL 中使用浮点数和十进制数据类型有什么区别?.

What difference does it make when I use float and decimal data types in MySQL?.

我应该什么时候使用哪个?

When should I use which?

推荐答案

这个是我遇到这个时发现的怀疑.

This is what I found when I had this doubt.

mysql> create table numbers (a decimal(10,2), b float);
mysql> insert into numbers values (100, 100);
mysql> select @a := (a/3), @b := (b/3), @a * 3, @b * 3 from numbers \G
*************************** 1. row ***************************
  @a := (a/3): 33.333333333
  @b := (b/3): 33.333333333333
@a + @a + @a: 99.999999999000000000000000000000
@b + @b + @b: 100

小数点在这种情况下完成了应该做的事情,它截断了其余部分,从而失去了 1/3 部分.

The decimal did exactly what's supposed to do on this cases, it truncated the rest, thus losing the 1/3 part.

所以对于总和,小数更好,但对于除法,浮点数是当然,在某种程度上更好.我的意思是,使用 DECIMAL 不会给无论如何,你都是一个失败证明算法".

So for sums the decimal is better, but for divisions the float is better, up to some point, of course. I mean, using DECIMAL will not give you a "fail proof arithmetic" in any means.

希望这会有所帮助.

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