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
UNIX时间戳只是一个特定日期和UNIX纪元之间的秒数，
SELECT DATEDIFF(SECOND，{d '1970-01-01'}，GETDATE()) //返回SQL server中的UNIX时间戳
你可以创建一个函数，使用Country Offset将本地日期时间转换为Unix UTC SQL server中的Unix时间戳函数
该函数将UTC时间转换为EST时间，并进行DST调整。你可以在这个函数中更改你设计的时区名称，或者从注册表中获取:
Create Function fnConvertUTCTimetoESTTime(
@UTCTime as datetime
)
returns datetime
as
begin
return convert(datetime, convert(varchar(23), @UTCTime AT TIME ZONE 'UTC' AT TIME ZONE 'Eastern Standard Time', 121), 121)
end
go
select dbo.fnConvertUTCTimetoESTTime ('2020-3-8 5:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-3-8 6:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-3-8 7:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-3-8 8:00:00.000')
--returns 0:00am, 1:00am, 3:00am, 4:00am
select dbo.fnConvertUTCTimetoESTTime ('2020-11-1 4:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-11-1 5:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-11-1 6:00:00.000')
, dbo.fnConvertUTCTimetoESTTime ('2020-11-1 7:00:00.000')
--returns 0:00am, 1:00am, 1:00am, 2:00am
请注意，您不能只是返回“@UTCTime AT TIME ZONE 'UTC' AT TIME ZONE 'Eastern Standard TIME '”作为结果，因为该结果实际上是EST格式的UTC时间(当您比较这个“假”EST时间或将其包含在order子句中时，它将被转换回UTC时间)。
你可以在SQL Server 2008或更高版本上这样做:
SELECT CONVERT(datetime,
SWITCHOFFSET(CONVERT(datetimeoffset,
MyTable.UtcColumn),
DATENAME(TzOffset, SYSDATETIMEOFFSET())))
AS ColumnInLocalTime
FROM MyTable
你也可以用更简洁的方法:
SELECT DATEADD(mi, DATEDIFF(mi, GETUTCDATE(), GETDATE()), MyTable.UtcColumn)
AS ColumnInLocalTime
FROM MyTable
无论您做什么，都不要使用-来减去日期，因为该操作不是原子的，并且由于在不同时间(即非原子地)检查的系统datetime和本地datetime之间的竞争条件，您有时会得到不确定的结果。
请注意，这个答案没有考虑夏令时。如果你想包含夏令时调整，也请参阅以下SO问题:
如何在SQL Server中创建夏令时开始和结束函数
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
我有代码执行UTC到本地和本地到UTC时间，允许使用这样的代码进行转换
DECLARE @usersTimezone VARCHAR(32)='Europe/London'
DECLARE @utcDT DATETIME=GetUTCDate()
DECLARE @userDT DATETIME=[dbo].[funcUTCtoLocal](@utcDT, @usersTimezone)
and
DECLARE @usersTimezone VARCHAR(32)='Europe/London'
DECLARE @userDT DATETIME=GetDate()
DECLARE @utcDT DATETIME=[dbo].[funcLocaltoUTC](@userDT, @usersTimezone)
这些函数可以支持NodaTime提供的IANA/TZDB中的全部或一部分时区-请参阅https://nodatime.org/TimeZones上的完整列表
请注意，我的用例意味着我只需要一个“当前”窗口，允许在大约+/- 5年的范围内转换时间。这意味着，如果您需要很宽的时间段，我使用的方法可能不适合您，因为它在给定日期范围内为每个时区间隔生成代码的方式不同。
该项目位于GitHub: https://github.com/elliveny/SQLServerTimeConversion
这将生成如下示例所示的SQL函数代码
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