【叶子函数分享四十一】SQL位移运算函数

-- =============================================
-- Author: <maco_wang>
-- Create date: <2011-03-22>
-- Description: <SQL位移运算函数>
-- =============================================
go
--创建函数
create function displacement(@n as bigint,@m as varchar(3))
returns int
as
begin
declare @maco varchar(50);set @maco=''
declare @i int
declare @x int
declare @s int
while (@n<>0)
begin
set @maco=@maco+convert(char(1),@n%2)
set @n=@n/2
end
set @maco=reverse(@maco)
set @maco=RIGHT('0000'+@maco,4)
set @s=LEN(@maco)
set @i=convert(int,RIGHT(@m,1))
set @x=1
if LEFT(@m,2)='<<'
begin
while(@x<=@i)
begin
select @maco=@maco+'0'
select @x=@x+1
end
select @maco=RIGHT(@maco,@s)
end
if LEFT(@m,2)='>>'
begin
while(@x<=@i)
begin
select @maco='0'+@maco
select @x=@x+1
end
select @maco=LEFT(@maco,@s)
end
set @i=LEN(@maco)
set @s=0
while(@i>0)
begin
if SUBSTRING(@maco,LEN(@maco)-@i+1,1)='1'
begin
select @s=@s+POWER(2,convert(float,@i-1))
end
select @i=@i-1
end
return @s
end

--测试示例
select dbo.displacement(1,'<<3')
select dbo.displacement(8,'>>1')
select dbo.displacement(12,'>>3')

--运行结果
/*
8
4
1
*/