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
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
其他回答
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')))
下面的版本考虑了夏令时、UTC抵消,并且没有锁定到特定的年份。
---------------------------------------------------------------------------------------------------
--Name: udfToLocalTime.sql
--Purpose: To convert UTC to local US time accounting for DST
--Author: Patrick Slesicki
--Date: 3/25/2014
--Notes: Works on SQL Server 2008R2 and later, maybe SQL Server 2008 as well.
-- Good only for US States observing the Energy Policy Act of 2005.
-- Function doesn't apply for years prior to 2007.
-- Function assumes that the 1st day of the week is Sunday.
--Tests:
-- SELECT dbo.udfToLocalTime('2014-03-09 9:00', DEFAULT)
-- SELECT dbo.udfToLocalTime('2014-03-09 10:00', DEFAULT)
-- SELECT dbo.udfToLocalTime('2014-11-02 8:00', DEFAULT)
-- SELECT dbo.udfToLocalTime('2014-11-02 9:00', DEFAULT)
---------------------------------------------------------------------------------------------------
ALTER FUNCTION udfToLocalTime
(
@UtcDateTime AS DATETIME
,@UtcOffset AS INT = -8 --PST
)
RETURNS DATETIME
AS
BEGIN
DECLARE
@PstDateTime AS DATETIME
,@Year AS CHAR(4)
,@DstStart AS DATETIME
,@DstEnd AS DATETIME
,@Mar1 AS DATETIME
,@Nov1 AS DATETIME
,@MarTime AS TIME
,@NovTime AS TIME
,@Mar1Day AS INT
,@Nov1Day AS INT
,@MarDiff AS INT
,@NovDiff AS INT
SELECT
@Year = YEAR(@UtcDateTime)
,@MarTime = CONVERT(TIME, DATEADD(HOUR, -@UtcOffset, '1900-01-01 02:00'))
,@NovTime = CONVERT(TIME, DATEADD(HOUR, -@UtcOffset - 1, '1900-01-01 02:00'))
,@Mar1 = CONVERT(CHAR(16), @Year + '-03-01 ' + CONVERT(CHAR(5), @MarTime), 126)
,@Nov1 = CONVERT(CHAR(16), @Year + '-11-01 ' + CONVERT(CHAR(5), @NovTime), 126)
,@Mar1Day = DATEPART(WEEKDAY, @Mar1)
,@Nov1Day = DATEPART(WEEKDAY, @Nov1)
--Get number of days between Mar 1 and DST start date
IF @Mar1Day = 1 SET @MarDiff = 7
ELSE SET @MarDiff = 15 - @Mar1Day
--Get number of days between Nov 1 and DST end date
IF @Nov1Day = 1 SET @NovDiff = 0
ELSE SET @NovDiff = 8 - @Nov1Day
--Get DST start and end dates
SELECT
@DstStart = DATEADD(DAY, @MarDiff, @Mar1)
,@DstEnd = DATEADD(DAY, @NovDiff, @Nov1)
--Change UTC offset if @UtcDateTime is in DST Range
IF @UtcDateTime >= @DstStart AND @UtcDateTime < @DstEnd SET @UtcOffset = @UtcOffset + 1
--Get Conversion
SET @PstDateTime = DATEADD(HOUR, @UtcOffset, @UtcDateTime)
RETURN @PstDateTime
END
GO
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
对于Azure SQL和@@Version >= SQL Server 2016用户,下面是一个使用AT TIME ZONE的简单函数。
CREATE FUNCTION [dbo].[Global_Convert_UTCTimeTo_LocalTime]
(
@LocalTimeZone VARCHAR(50),
@UTCDateTime DATETIME
)
RETURNS DATETIME
AS
BEGIN
DECLARE @ConvertedDateTime DATETIME;
SELECT @ConvertedDateTime = @UTCDateTime AT TIME ZONE 'UTC' AT TIME ZONE @LocalTimeZone
RETURN @ConvertedDateTime
END
GO
对于@LocalTimeZone可以采用的值类型,请转到此链接或转到KEY_LOCAL_MACHINE\SOFTWARE\Microsoft\Windows NT\CurrentVersion\Time Zones
我发现当有大量数据时,一次性函数的方法太慢了。因此,我通过连接到一个允许计算小时差的表函数来实现它,它基本上是带有小时偏移量的datetime分段。一年是4行。这个表格函数
dbo.fn_getTimeZoneOffsets('3/1/2007 7:00am', '11/5/2007 9:00am', 'EPT')
将返回这个表:
startTime endTime offset isHr2
3/1/07 7:00 3/11/07 6:59 -5 0
3/11/07 7:00 11/4/07 6:59 -4 0
11/4/07 7:00 11/4/07 7:59 -5 1
11/4/07 8:00 11/5/07 9:00 -5 0
它确实考虑了夏时制。下面是它如何使用的示例,完整的博客文章在这里。
select mt.startTime as startUTC,
dateadd(hh, tzStart.offset, mt.startTime) as startLocal,
tzStart.isHr2
from MyTable mt
inner join dbo.fn_getTimeZoneOffsets(@startViewUTC, @endViewUTC, @timeZone) tzStart
on mt.startTime between tzStart.startTime and tzStart.endTime
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