sql-server - 如何根据格林威治标准时间计算当地时间？

Question

我正在尝试根据我为他们提供的 GMT 时间数据来计算各个国家/地区的当地时间。我还需要知道他们是否也遵守夏令时。有没有办法在没有 CLR 的情况下实现这一目标？这里有一些示例数据供您参考。

DDL：

CREATE TABLE #Temp(
COUNTRY_CODE VARCHAR(2)
DATETIME VARCHAR(50)
);

DML：

INSERT INTO #Temp(COUNTRY_CODE, DATETIME)
VALUES
('EE', 'Sun Mar 29 00:00:00 GMT 1992'),
('AZ', 'Sun Mar 28 00:00:00 GMT 1993'),
('CZ', 'Sun Mar 27 00:00:00 GMT 1994'),
('DE', 'Sun Mar 26 00:00:00 GMT 1995'),
('AD', 'Sun Mar 31 00:00:00 GMT 1996'),
('GI', 'Sun Mar 30 00:00:00 GMT 1997'),
('DK', 'Sun Mar 29 00:00:00 GMT 1998'),
('AL', 'Sun Mar 28 00:00:00 GMT 1999'),
('ES', 'Sun Mar 26 00:00:00 GMT 2000'),
('LT', 'Sun Mar 25 00:00:00 GMT 2001');

环境： Microsoft Azure SQL 数据仓库 - 10.0.10783.0 Oct 26 2019 23:24:02 版权所有 (c) Microsoft Corporation

谢谢！

Answer 1

这很混乱，因为您的数据是。您还有很长的路要走，我建议实际上将您的“ DateTime”列更改为正确的数据类型，而不是使用计算列：

--Create sample table
CREATE TABLE dbo.YourTable (CountryCode char(2),
                            NotADateTime varchar(50));

INSERT INTO dbo.YourTable (CountryCode,
                           NotADateTime)
VALUES ('EE', 'Sun Mar 29 00:00:00 GMT 1992'),
       ('AZ', 'Sun Mar 28 00:00:00 GMT 1993'),
       ('CZ', 'Sun Mar 27 00:00:00 GMT 1994'),
       ('DE', 'Sun Mar 26 00:00:00 GMT 1995'),
       ('AD', 'Sun Mar 31 00:00:00 GMT 1996'),
       ('GI', 'Sun Mar 30 00:00:00 GMT 1997'),
       ('DK', 'Sun Mar 29 00:00:00 GMT 1998'),
       ('AL', 'Sun Mar 28 00:00:00 GMT 1999'),
       ('ES', 'Sun Mar 26 00:00:00 GMT 2000'),
       ('LT', 'Sun Mar 25 00:00:00 GMT 2001'),
       ('FR', 'Sun Jul 14 00:00:00 GMT 2019'); --Add one that is in DST.
GO
--Create a proper datetimeoffset column
ALTER TABLE dbo.YourTable ADD ADateTime AS TRY_CONVERT(datetimeoffset(0),RIGHT(NotADateTime,4) + '-' +
                                                                         CASE SUBSTRING(NotADateTime,5,3) WHEN 'Jan' THEN '01'
                                                                                                             WHEN 'Feb' THEN '02'
                                                                                                             WHEN 'Mar' THEN '03'
                                                                                                             WHEN 'Apr' THEN '04'
                                                                                                             WHEN 'May' THEN '05'
                                                                                                             WHEN 'Jun' THEN '06'
                                                                                                             WHEN 'Jul' THEN '07'
                                                                                                             WHEN 'Aug' THEN '08'
                                                                                                             WHEN 'Sep' THEN '09'
                                                                                                             WHEN 'Oct' THEN '10'
                                                                                                             WHEN 'Nov' THEN '11'
                                                                                                             WHEN 'Dec' THEN '12'
                                                                         END + '-' + SUBSTRING(NotADateTime,9,2) + 'T' +
                                                                         SUBSTRING(NotADateTime,12,9));

GO
--Check data
SELECT YT.CountryCode,
       YT.NotADateTime,
       YT.ADateTime
FROM dbo.YourTable YT;
GO     
--Add a timezone lookup table
CREATE TABLE dbo.TimeZoneLookup (CountryCode char(2),
                                 MSTimeZoneName nvarchar(128));
INSERT INTO dbo.TimeZoneLookup (CountryCode,
                                MSTimeZoneName)
SELECT CountryCode,'Central Europe Standard Time' --All apepar to be european countries, so jsut assumed. You should NOT. 
FROM dbo.YourTable; --You can find all the timezones in sys.time_zone_info


GO
--JOIN and change timezone
SELECT YT.CountryCode,
       YT.ADateTime,
       YT.ADateTime AT TIME ZONE TZ.MSTimeZoneName
FROM dbo.YourTable YT
     JOIN dbo.TimeZoneLookup TZ ON YT.CountryCode = TZ.CountryCode

GO
--Clean up
DROP TABLE dbo.YourTable;
DROP TABLE dbo.TimeZoneLookup;