根据0~20的与运算总结

 1 Create FUNCTION DecToBin(@Dec Int)
 2 RETURNS VARCHAR(16)
 3 AS
 4 begin
 5  declare @BinStr as varchar(20)
 6  declare @Mod2 as int 
 7  declare @Div2   as int
 8 
 9  
10 
11  set @Div2 = @Dec / 2
12  set @Mod2 = @Dec % 2
13  set @BinStr=‘‘
14 
15  
16 
17  while @Div2<>0
18  begin
19   if @Mod2=0 
20    set @BinStr = @BinStr + ‘0‘
21   else 
22    set @BinStr = @BinStr + ‘1‘
23  
24   set @Dec = @Dec / 2
25   set @Div2 = @Dec / 2
26   set @Mod2 = @Dec % 2 
27  end
28  
29  set @BinStr = @BinStr + ‘1‘
30  
31  return REVERSE(@BinStr + right(‘0000000000000000‘,16-len(@BinStr)))
32 end