为什么在SQL Server中四舍五入为从float到varchar [英] Why casting from float to varchar is being rounded in SQL Server

问题描述

下面的sql

  declare @a as float，@b as float 
 
 select @a （@a as VARCHAR（40））AS a_float_to_varchar，
 CAST（@b as VARCHAR（40））AS b_float_to_varchar 
 <= $ 1.353954 
 select 
 CAST / code> 

结果



  a_float_to_varchar b_float_to_varchar 
 ---------------------------------------- ---- ------------------------------------ 
 1.35395 1.35396 
  
 
 
基于
 
 
  http://msdn.microsoft.com/en-us/library/ms173773.aspx  
 
 
 
 float的精度为15位数，所以我不确定为什么数字被转换为varchar时被舍入为解决方案

同样来自您的链接（实际上是第一行）：



近似数字数据类型...

如果您需要精确的精度，请不要使用 float 。



这就是说，有一个函数 STR（）专门用于将 float 转换为字符数据类型。

Following sql

declare @a as float, @b as float

select @a=1.353954 , @b=1.353956
select 
CAST(@a as VARCHAR(40)) AS a_float_to_varchar ,
CAST(@b as VARCHAR(40)) AS b_float_to_varchar

results in

a_float_to_varchar                       b_float_to_varchar
---------------------------------------- ----------------------------------------
1.35395                                  1.35396

based on

http://msdn.microsoft.com/en-us/library/ms173773.aspx

float has precision of 15 digits so I am not sure why the number is being rounded when converted to varchar

解决方案

Also from your link (it's actually the first line):

Approximate-number data types...

If you want exact precision, don't use float.

That being said, there is a function STR() specifically for converting float to a character data type.

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