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declare @OldTime datetime
set @oldTime =getdate()
select dateadd(hh,-3,@oldtime)
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MS    MILLISECOND
SS,S   SECOND
MI,N  MINUTE
HH    HOUR
DW,W     WEEKDAY
WK,WW   WEEK
DD,D  DAY
DY,Y   DAY
DY,Y   DAY OF YEAR
MM,N  MONTH
QQ,Q  QUARTER
YY,YYYY  YEAR
 
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DETEDIFF(DATEPART,STARTDATE,ENDDATE)
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CASE WHEN EXISTS (SELECT 1 from dbo.sysindexes si INNER JOIN dbo.sysindexkeys sik ON si.id = sik.id
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/*
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sql²éÕÒij¸ö×Ö·û´®µÚN´Î³öÏÖµÄλÖõĺ¯Êý(תÌû)

if exists(select 1 from sysobjects where name='char_index')
drop function char_index
create function char_index(@string varchar(8000),@char varchar(10),@index smallint)
--@string:´ý²éÕÒ×Ö·û´®£¬@index:²éÕÒλÖÃ
returns smallint
as
begin
  declare
  @i tinyint,--µ±Ç°ÕÒµ½µÚ@i¸ö
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