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
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
其他回答
第一个功能:配置为意大利时区(+1，+2)，切换日期:3月和10月的最后一个星期天，返回当前时区与datetime的差值作为参数。
Returns:
current timezone < parameter timezone ==> +1
current timezone > parameter timezone ==> -1
else 0
代码是:
CREATE FUNCTION [dbo].[UF_ADJUST_OFFSET]
(
@dt_utc datetime2(7)
)
RETURNS INT
AS
BEGIN
declare @month int,
@year int,
@current_offset int,
@offset_since int,
@offset int,
@yearmonth varchar(8),
@changeoffsetdate datetime2(7)
declare @lastweek table(giorno datetime2(7))
select @current_offset = DATEDIFF(hh, GETUTCDATE(), GETDATE())
select @month = datepart(month, @dt_utc)
if @month < 3 or @month > 10 Begin Set @offset_since = 1 Goto JMP End
if @month > 3 and @month < 10 Begin Set @offset_since = 2 Goto JMP End
--If i'm here is march or october
select @year = datepart(yyyy, @dt_utc)
if @month = 3
Begin
Set @yearmonth = cast(@year as varchar) + '-03-'
Insert Into @lastweek Values(@yearmonth + '31 03:00:00.000000'),(@yearmonth + '30 03:00:00.000000'),(@yearmonth + '29 03:00:00.000000'),(@yearmonth + '28 03:00:00.000000'),
(@yearmonth + '27 03:00:00.000000'),(@yearmonth + '26 03:00:00.000000'),(@yearmonth + '25 03:00:00.000000')
--Last week of march
Select @changeoffsetdate = giorno From @lastweek Where datepart(weekday, giorno) = 1
if @dt_utc < @changeoffsetdate
Begin
Set @offset_since = 1
End Else Begin
Set @offset_since = 2
End
End
if @month = 10
Begin
Set @yearmonth = cast(@year as varchar) + '-10-'
Insert Into @lastweek Values(@yearmonth + '31 03:00:00.000000'),(@yearmonth + '30 03:00:00.000000'),(@yearmonth + '29 03:00:00.000000'),(@yearmonth + '28 03:00:00.000000'),
(@yearmonth + '27 03:00:00.000000'),(@yearmonth + '26 03:00:00.000000'),(@yearmonth + '25 03:00:00.000000')
--Last week of october
Select @changeoffsetdate = giorno From @lastweek Where datepart(weekday, giorno) = 1
if @dt_utc > @changeoffsetdate
Begin
Set @offset_since = 1
End Else Begin
Set @offset_since = 2
End
End
JMP:
if @current_offset < @offset_since Begin
Set @offset = 1
End Else if @current_offset > @offset_since Set @offset = -1 Else Set @offset = 0
Return @offset
END
然后是转换日期的函数
CREATE FUNCTION [dbo].[UF_CONVERT]
(
@dt_utc datetime2(7)
)
RETURNS datetime
AS
BEGIN
declare @offset int
Select @offset = dbo.UF_ADJUST_OFFSET(@dt_utc)
if @dt_utc >= '9999-12-31 22:59:59.9999999'
set @dt_utc = '9999-12-31 23:59:59.9999999'
Else
set @dt_utc = (SELECT DATEADD(mi, DATEDIFF(mi, GETUTCDATE(), GETDATE()), @dt_utc) )
if @offset <> 0
Set @dt_utc = dateadd(hh, @offset, @dt_utc)
RETURN @dt_utc
END
这些对我来说都没用，但下面这个100%有效。希望这能帮助其他像我一样尝试转换它的人。
CREATE FUNCTION [dbo].[fn_UTC_to_EST]
(
@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 = DATEADD(dd,7 + (6-(DATEDIFF(dd,0,DATEADD(mm,(YEAR(GETDATE())-1900) * 12 + 2,0))%7)),DATEADD(mm,(YEAR(GETDATE())-1900) * 12 + 2,0))+'02:00:00'
set @FSN = DATEADD(dd, (6-(DATEDIFF(dd,0,DATEADD(mm,(YEAR(GETDATE())-1900) * 12 + 10,0))%7)),DATEADD(mm,(YEAR(GETDATE())-1900) * 12 + 10,0)) +'02:00:00'
-- 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
如果您将数据存储为UTC日期在数据库中，您可以做一些简单的事情
select
[MyUtcDate] + getdate() - getutcdate()
from [dbo].[mytable]
这是从服务器的角度来看，它总是本地的，你不会笨拙地使用AT TIME ZONE '你的时区名称'， 如果您的数据库像客户端安装一样被移动到另一个时区，那么硬编码的时区可能会让您感到困扰。
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
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