SQL Server 2008和毫秒 [英] SQL Server 2008 and milliseconds
本文介绍了SQL Server 2008和毫秒的处理方法，对大家解决问题具有一定的参考价值，需要的朋友们下面随着小编来一起学习吧！
问题描述
在SQL Server 2008中，为什么以下查询返回相同的值？
In SQL Server 2008, why do the following queries return the same value?
-- These all return 2011-01-01 23:59:59.997
SELECT CAST('2011-01-01 23:59:59.997' as datetime)
SELECT CAST('2011-01-01 23:59:59.998' as datetime)
为什么以下查询到第二天？
And why does the following query round to the next day?
-- Returns 2011-01-02 00:00:00.000
SELECT CAST('2011-01-01 23:59:59.999' as datetime)
推荐答案
SQL Server中DateTime的准确性一直是到1/300秒（3.33ms），所以任何不分精度的值都会被舍入。
The accuracy of DateTime within SQL Server has always been to 1/300s of a second (3.33ms), so any value that does not divide precisely gets rounded.
- 997保持原样
- 998将轮到997
- 999将最多可以达到000
为了获得更多的准确性，有SQL Server 2008以后的DateTime2数据类型可以精确到小数点后7位。
To get additional accuracy, there is the DateTime2 data type, available in SQL Server 2008 onwards, that can be accurate to 7 decimal places.
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