按每小时(每半小时)对数据进行抽取的通用SQL循环语句

(一)
declare @begin_date as smalldatetime select @begin_date = '07/27/2006 00:00:00'
declare @i as int  select @i=0
while   dateadd(hh,@i,@begin_date) < '07/27/2006 12:00:00'
begin
   select @i as code,dateadd(hh,@i,@begin_date) as jdate
   set @i=@i+1
end

(二)
declare @begin_date smalldatetime select @begin_date = '07/27/2006 00:00:00'
declare @i          int           select @i=0
while   dateadd(n,@i,@begin_date) < getdate()
begin
     select @i,dateadd(n,@i,@begin_date) jdate
     set @i=@i+30
end