我正在做一些SQL选择查询,并希望将我的UTC日期时间列转换为本地时间,以便在我的查询结果中显示为本地时间。注意,我不希望通过代码进行这种转换,而是当我对我的数据库进行手动和随机SQL查询时。
当前回答
这可以在没有函数的情况下完成。下面的代码将把UTC时间转换为考虑夏令时的山地时间。相应地调整所有的-6和-7数字到您的时区(即对于EST,您将分别调整为-4和-5)
--Adjust a UTC value, in the example the UTC field is identified as UTC.Field, to account for daylight savings time when converting out of UTC to Mountain time.
CASE
--When it's between March and November, it is summer time which is -6 from UTC
WHEN MONTH ( UTC.Field ) > 3 AND MONTH ( UTC.Field ) < 11
THEN DATEADD ( HOUR , -6 , UTC.Field )
--When its March and the day is greater than the 14, you know it's summer (-6)
WHEN MONTH ( UTC.Field ) = 3
AND DATEPART ( DAY , UTC.Field ) >= 14
THEN
--However, if UTC is before 9am on that Sunday, then it's before 2am Mountain which means it's still Winter daylight time.
CASE
WHEN DATEPART ( WEEKDAY , UTC.Field ) = 1
AND UTC.Field < '9:00'
--Before 2am mountain time so it's winter, -7 hours for Winter daylight time
THEN DATEADD ( HOUR , -7 , UTC.Field )
--Otherwise -6 because it'll be after 2am making it Summer daylight time
ELSE DATEADD ( HOUR , -6 , UTC.Field )
END
WHEN MONTH ( UTC.Field ) = 3
AND ( DATEPART ( WEEKDAY , UTC.Field ) + 7 ) <= DATEPART ( day , UTC.Field )
THEN
--According to the date, it's moved onto Summer daylight, but we need to account for the hours leading up to 2am if it's Sunday
CASE
WHEN DATEPART ( WEEKDAY , UTC.Field ) = 1
AND UTC.Field < '9:00'
--Before 9am UTC is before 2am Mountain so it's winter Daylight, -7 hours
THEN DATEADD ( HOUR , -7 , UTC.Field )
--Otherwise, it's summer daylight, -6 hours
ELSE DATEADD ( HOUR , -6 , UTC.Field )
END
--When it's November and the weekday is greater than the calendar date, it's still Summer so -6 from the time
WHEN MONTH ( UTC.Field ) = 11
AND DATEPART ( WEEKDAY , UTC.Field ) > DATEPART ( DAY , UTC.Field )
THEN DATEADD ( HOUR , -6 , UTC.Field )
WHEN MONTH ( UTC.Field ) = 11
AND DATEPART ( WEEKDAY , UTC.Field ) <= DATEPART ( DAY , UTC.Field )
--If the weekday is less than or equal to the calendar day it's Winter daylight but we need to account for the hours leading up to 2am.
CASE
WHEN DATEPART ( WEEKDAY , UTC.Field ) = 1
AND UTC.Field < '8:00'
--If it's before 8am UTC and it's Sunday in the logic outlined, then it's still Summer daylight, -6 hours
THEN DATEADD ( HOUR , -6 , UTC.Field )
--Otherwise, adjust for Winter daylight at -7
ELSE DATEADD ( HOUR , -7 , UTC.Field )
END
--If the date doesn't fall into any of the above logic, it's Winter daylight, -7
ELSE
DATEADD ( HOUR , -7 , UTC.Field )
END
其他回答
下面是一个将夏令时考虑在内的更简单的例子
CREATE FUNCTION [dbo].[UtcToLocal]
(
@p_utcDatetime DATETIME
)
RETURNS DATETIME
AS
BEGIN
RETURN DATEADD(MINUTE, DATEDIFF(MINUTE, GETUTCDATE(), @p_utcDatetime), GETDATE())
END
我没有发现任何这些示例有助于将日期时间存储为UTC到指定时区(不是服务器的时区,因为Azure SQL数据库以UTC运行)中的日期时间。我是这样处理的。它并不优雅,但它很简单,无需维护其他表就能给出正确答案:
select CONVERT(datetime, SWITCHOFFSET(dateTimeField, DATEPART(TZOFFSET,
dateTimeField AT TIME ZONE 'Eastern Standard Time')))
您必须重新格式化字符串以及转换为正确的时间。在这种情况下,我需要祖鲁时间。
Declare @Date datetime;
Declare @DateString varchar(50);
set @Date = GETDATE();
declare @ZuluTime datetime;
Declare @DateFrom varchar (50);
Declare @DateTo varchar (50);
set @ZuluTime = DATEADD(second, DATEDIFF(second, GETDATE(), GETUTCDATE()), @Date);
set @DateString = FORMAT(@ZuluTime, 'yyyy-MM-ddThh:mm:ssZ', 'en-US' )
select @DateString;
罗恩的回答有一个错误。它使用当地时间凌晨2:00,其中需要UTC等效值。我没有足够的声望分数来评论Ron的回答,所以更正版本如下:
-- =============================================
-- Author: Ron Smith
-- Create date: 2013-10-23
-- Description: Converts UTC to DST
-- based on passed Standard offset
-- =============================================
CREATE FUNCTION [dbo].[fn_UTC_to_DST]
(
@UTC datetime,
@StandardOffset int
)
RETURNS datetime
AS
BEGIN
declare
@DST datetime,
@SSM datetime, -- Second Sunday in March
@FSN datetime -- First Sunday in November
-- get DST Range
set @SSM = datename(year,@UTC) + '0314'
set @SSM = dateadd(hour,2 - @StandardOffset,dateadd(day,datepart(dw,@SSM)*-1+1,@SSM))
set @FSN = datename(year,@UTC) + '1107'
set @FSN = dateadd(second,-1,dateadd(hour,2 - (@StandardOffset + 1),dateadd(day,datepart(dw,@FSN)*-1+1,@FSN)))
-- add an hour to @StandardOffset if @UTC is in DST range
if @UTC between @SSM and @FSN
set @StandardOffset = @StandardOffset + 1
-- convert to DST
set @DST = dateadd(hour,@StandardOffset,@UTC)
-- return converted datetime
return @DST
END
我发现这个函数比使用单独的表或循环的其他解决方案更快。这只是一个基本的case语句。考虑到4月到10月之间的所有月份都有-4小时的偏移(东部时间),我们只需要为边缘日添加更多的案例线。否则,偏移量为-5小时。
这是特定于从UTC到东部时间的转换,但可以根据需要添加其他时区功能。
USE [YourDatabaseName]
GO
/****** Object: UserDefinedFunction [dbo].[ConvertUTCtoEastern] Script Date: 11/2/2016 5:21:52 PM ******/
SET ANSI_NULLS ON
GO
SET QUOTED_IDENTIFIER ON
GO
CREATE FUNCTION [dbo].[ConvertUTCtoEastern]
(
@dtStartDate DATETIME
)
RETURNS DATETIME
AS
BEGIN
DECLARE @Working DATETIME
DECLARE @Returned DATETIME
SET @Working = @dtStartDate
SET @Working =
case when month(@Working) between 4 and 10 then dateadd(HH,-4,@Working)
when @Working between '2017-03-12' and '2017-11-05' then dateadd(HH,-4,@Working)
when @Working between '2016-03-13' and '2016-11-06' then dateadd(HH,-4,@Working)
when @Working between '2015-03-08' and '2015-11-01' then dateadd(HH,-4,@Working)
when @Working between '2014-03-09' and '2014-11-02' then dateadd(HH,-4,@Working)
when @Working between '2013-03-10' and '2013-11-03' then dateadd(HH,-4,@Working)
when @Working between '2012-03-11' and '2012-11-04' then dateadd(HH,-4,@Working)
else dateadd(HH,-5,@Working) end
SET @Returned = @Working
RETURN @Returned
END
GO