对甲骨文来说最好的方法:

硬编码的datetime:

SELECT TO_CHAR(CAST((FROM_TZ(CAST(TO_DATE('2018-10-27 21:00', 'YYYY-MM-DD HH24:MI') AS TIMESTAMP), 'UTC') AT  TIME ZONE 'EET') AS DATE), 'YYYY-MM-DD HH24:MI') UTC_TO_EET FROM DUAL

结果: 2018-10-28 00:00

列名和表名:

SELECT TO_CHAR(CAST((FROM_TZ(CAST(COLUMN_NAME AS TIMESTAMP), 'UTC') AT  TIME ZONE 'EET') AS DATE), 'YYYY-MM-DD HH24:MI') UTC_TO_EET FROM TABLE_NAME

对于任何仍然试图解决这个问题的人，这里有一个在SQL Server 2017中工作的概念证明

 declare
    @StartDate date = '2020-01-01'

;with cte_utc as
(
    select 
         1 as i
        ,CONVERT(datetime, @StartDate) AS UTC
        ,datepart(weekday, CONVERT(datetime, @StartDate)) as Weekday
        ,datepart(month, CONVERT(datetime, @StartDate)) as [Month]
        ,datepart(YEAR, CONVERT(datetime, @StartDate)) as [Year]
        
    union all

    Select
         i + 1
        ,dateadd(d, 1, utc)
        ,datepart(weekday, CONVERT(datetime, dateadd(d, 1, utc))) as Weekday
        ,datepart(month, CONVERT(datetime, dateadd(d, 1, utc))) as [Month]
        ,datepart(YEAR, CONVERT(datetime, dateadd(d, 1, utc))) as [Year]
    from    
        cte_utc
    where
        (i + 1) < 32767

), cte_utc_dates as 
(
    select 
        *,
        DENSE_RANK()OVER(PARTITION BY [Year], [Month], [Weekday] ORDER BY Utc) WeekDayIndex
    from
        cte_utc

), cte_hours as (
    select 0 as [Hour]
    union all
    select [Hour] + 1 from cte_hours where [Hour] < 23
)

select
    d.*
    , DATEADD(hour, h.Hour, d.UTC) AS UtcTime
    ,CONVERT(datetime, DATEADD(hour, h.Hour, d.UTC) AT TIME ZONE 'UTC' AT TIME ZONE 'Central Standard Time') CST
    ,CONVERT(datetime, DATEADD(hour, h.Hour, d.UTC) AT TIME ZONE 'UTC' AT TIME ZONE 'Eastern Standard Time') EST
from
    cte_utc_dates d, cte_hours h
where
    ([Month] = 3 and [Weekday] = 1 and WeekDayIndex = 2 )-- dst start
    or 
    ([Month] = 11 and [Weekday] = 1 and WeekDayIndex = 1 )-- dst end
order by
    utc
OPTION (MAXRECURSION 32767)

GO

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

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

没有一种简单的方法能以正确而通用的方式做到这一点。

首先，必须理解偏移量取决于所讨论的日期、时区和夏令时。 GetDate()-GetUTCDate只提供今天服务器TZ的偏移量，这是不相关的。

我只见过两种有效的解决方案，我已经搜索了很多。

1)一个自定义SQL函数，包含几个基本数据表，如每个TZ的时区和夏令时规则。 工作，但不是很优雅。我不能发布，因为我没有代码。

编辑:下面是这个方法的一个例子 https://gist.github.com/drumsta/16b79cee6bc195cd89c8

2)添加一个.net程序集到db， .net可以很容易地做到这一点。这工作得很好，但缺点是你需要在服务器级配置几个参数，配置很容易被破坏，例如，如果你恢复数据库。 我使用这个方法，但我不能张贴它，因为我没有自己的代码。

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