检查是否启用了夏令时

Question

在一种情况下，我必须检查夏令时是否有效。根据检查的结果，我必须在SQL Server过程中进行一些计算。

快速检查当前是否已实施夏令时的最佳方法是什么？

Answer 1

我在 Tim Cullen创建的SQL Server中使用了该夏令时功能。

具体来说，我使用的代码是：

开始日期功能

CREATE function [dbo].[fn_GetDaylightSavingsTimeStart]
(@Year varchar(4))
RETURNS smalldatetime
as
begin
declare @DTSStartWeek smalldatetime, @DTSEndWeek smalldatetime
set @DTSStartWeek = '03/01/' + convert(varchar,@Year)
return case datepart(dw,@DTSStartWeek)
when 1 then
dateadd(hour,170,@DTSStartWeek)
when 2 then
dateadd(hour,314,@DTSStartWeek)
when 3 then 
dateadd(hour,290,@DTSStartWeek)
when 4 then 
dateadd(hour,266,@DTSStartWeek)
when 5 then 
dateadd(hour,242,@DTSStartWeek)
when 6 then 
dateadd(hour,218,@DTSStartWeek)
when 7 then
dateadd(hour,194,@DTSStartWeek)
end
end

结束日期功能

CREATE function [dbo].[fn_GetDaylightSavingsTimeEnd]
(@Year varchar(4))
RETURNS smalldatetime
as
begin
declare @DTSEndWeek smalldatetime
set @DTSEndWeek = '11/01/' + convert(varchar,@Year)
return case datepart(dw,dateadd(week,1,@DTSEndWeek))
when 1 then
dateadd(hour,2,@DTSEndWeek)
when 2 then
dateadd(hour,146,@DTSEndWeek)
when 3 then
dateadd(hour,122,@DTSEndWeek)
when 4 then
dateadd(hour,98,@DTSEndWeek)
when 5 then 
dateadd(hour,74,@DTSEndWeek)
when 6 then 
dateadd(hour,50,@DTSEndWeek)
when 7 then 
dateadd(hour,26,@DTSEndWeek)
end
end

然后，我在查询中使用如下功能：

declare @DLSStart smalldatetime 
, @DLSEnd smalldatetime 
, @DLSActive tinyint 
set @DLSStart = (select MSSQLTIPS.dbo.fn_GetDaylightSavingsTimeStart(convert(varchar,datepart(year,getdate()))))
set @DLSEnd = (select MSSQLTIPS.dbo.fn_GetDaylightSavingsTimeEnd(convert(varchar,datepart(year,getdate())))) 

if @Date between @DLSStart and @DLSEnd 
begin 
set @DLSActive = 1 
end 
else 
begin 
set @DLSActive = 0 
end 
select @DLSActive