在 SQL Server 中放置一个日期 [英] Floor a date in SQL server

问题描述

在 SQL Server 中，如何将 DATETIME 设置为秒/分钟/小时/天/年?

In SQL Server, how do I "floor" a DATETIME to the second/minute/hour/day/year?

假设我的日期是2008-09-17 12:56:53.430，那么地板的输出应该是:

Let's say that I have a date of 2008-09-17 12:56:53.430, then the output of flooring should be:

• 年份:2008-01-01 00:00:00.000
• 月份:2008-09-01 00:00:00.000
• 日:2008-09-17 00:00:00.000
• 时间:2008-09-17 12:00:00.000
• 分钟:2008-09-17 12:56:00.000
• 第二次:2008-09-17 12:56:53.000

推荐答案

关键是使用 DATEADD 和 DATEDIFF 以及适当的 SQL时间跨度枚举.

The key is to use DATEADD and DATEDIFF along with the appropriate SQL timespan enumeration.

declare @datetime datetime;
set @datetime = getdate();
select @datetime;
select dateadd(year,datediff(year,0,@datetime),0);
select dateadd(month,datediff(month,0,@datetime),0);
select dateadd(day,datediff(day,0,@datetime),0);
select dateadd(hour,datediff(hour,0,@datetime),0);
select dateadd(minute,datediff(minute,0,@datetime),0);
select dateadd(second,datediff(second,'2000-01-01',@datetime),'2000-01-01');
select dateadd(week,datediff(week,0,@datetime),-1); --Beginning of week is Sunday
select dateadd(week,datediff(week,0,@datetime),0); --Beginning of week is Monday

请注意，当您按秒计算时，如果您使用 0，通常会出现算术溢出.因此，请选择一个已知值，该值保证低于您尝试计算的日期时间.

Note that when you are flooring by the second, you will often get an arithmetic overflow if you use 0. So pick a known value that is guaranteed to be lower than the datetime you are attempting to floor.

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