一个好用的sql位移函数

CREATE FUNCTION [dbo].[BitMove](@long bigint,@operator varchar(3),@len int) 
RETURNS bigint AS 
BEGIN
 if @len=0
 return @long
 declare @i bigint
 declare @j bigint
 set @i=cast(0x8000000000000000 as bigint)
 set @j=cast(0x4000000000000000 as bigint)
 if @operator='<<'
 begin
 while @len>0
 begin
 set @len=@len-1
 if (@i&@long)=@i
 set @long=@long^@i
 if (@j&@long)=@j
 begin
 set @long=@long^@j
 set @long=@long*2
 if @len=0
 set @long=@long|@i
 end
 else
 set @long=@long*2
 end
 end
 else
 begin
 set @len=@len-1
 set @long=@long/2
 if @operator='>>>' and (@i&@long)=@i
 set @long=@long^@i
 set @long=@long/power(2,@len)
 end
 return @long
END