PostgreSQL-舍入浮点数 [英] PostgreSQL - rounding floating point numbers

问题描述

我在PostgreSQL 9.2中有一个关于浮点数的新手问题。

I have a newbie question about floating point numbers in PostgreSQL 9.2.

是否有一个函数可以直接舍入浮点数，即无需转换数字到数字类型？

Is there a function to round a floating point number directly, i.e. without having to convert the number to a numeric type first?

此外，我想知道是否存在以任意度量单位四舍五入的函数，例如最接近的0.05？

Also, I would like to know whether there is a function to round by an arbitrary unit of measure, such as to nearest 0.05?

首先将数字转换为小数形式时，以下查询可以正常工作：

When casting the number into a decimal form first, the following query works perfectly:

SELECT round(1/3.::numeric,4);

 round  
--------
 0.3333
(1 row)
Time: 0.917 ms

但是，我真正想要实现的是以下内容：

However, what really I'd like to achieve is something like the following:

SELECT round(1/3.::float,4);

当前会给我以下错误：

ERROR:  function round(double precision, integer) does not exist at character 8
Time: 0.949 ms

谢谢

推荐答案

您可以按照以下方式完成此操作

You can accomplish this by doing something along the lines of

select round( (21.04 /0.05 ),0)*0.05

其中 21.04 是要舍入的数字， 0.05 是准确性。

where 21.04 is the number to round and 0.05 is the accuracy.

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