T-SQL: 关于 Varbinary(Hex,Int) 与 Varchar(HexString) 之间的(数据类型)转换

T-SQL: 关于 Varbinary(Hex,Int) 与 Varchar(HexString) 之间的数据类型转换
我以前只是用存储过程简单地实现了:
16进制数的字符串表达 转变为 真正的16进制数:
例如: '0x5f' 转换成 16进制的 0x5f

declare  @  varbinary ( 8000 )
declare   @s   varchar ( 100 )
declare   @sql   nvarchar ( 100 )
set   @s   =   ' 0xFFFF '
set   @sql   =  N ' set @ =  '   +   cast ( @s   as   nvarchar ( 100 ))
exec  SP_EXECUTESQL  @sql  ,N ' @ varbinary(8000) out ' , @ out
select  @

该方法属于投机取巧,只实现了 HexString to Hex 的单向转换,而且不能用 "自定义函数(udf)" 实现!
利用这种方式还有一篇 blog@csdn: 实现了:

《用于执行(计算) "字符串表达式" 的 T-SQL 存储过程》
http://blog.csdn.net/playyuer/archive/2004/12/08/208601.aspx

今天在 google 搜到
http://www.google.com/search?hl=zh-CN&newwindow=1&q=HexToSMALLINT+HexToINT&btnG=%E6%90%9C%E7%B4%A2&lr=
现成儿的,这两篇好东西:

HexToInt
http://www.sqlservercentral.com/scripts/contributions/1495.asp

--  By Aaron West, 5/4/2005
--  This version allows negative numbers
CREATE   FUNCTION  dbo.HexToINT
(
  @Value   VARCHAR ( 8 )
)
RETURNS   INT
AS
BEGIN
    if   @Value   LIKE   ' %[^0-9A-Fa-f]% '
       RETURN   NULL
    DECLARE   @I   BIGINT
    SET   @I   =   CAST ( CAST ( RIGHT ( UPPER ( ' 00000000 '   +   @Value ), 8 )  AS   BINARY ( 8 ))  AS   BIGINT )  -   CAST ( 0x3030303030303030   AS   BIGINT )
    SET   @I = @I - (( @I / 16 ) & CAST ( 0x0101010101010101   AS   BIGINT )) * 7
    RETURN   CAST ( CAST (
                    ( @I & 15 )
                     + (( @I / 16 ) & 240 )
                     + (( @I / 256 ) & 3840 )
                     + (( @I / 4096 ) & 61440 )
                     + (( @I / 65536 ) & 983040 )
                     + (( @I / 1048576 ) & 15728640 )
                     + (( @I / 16777216 ) & 251658240 )
                     + ( @I / CAST ( 0x0100000000000000   AS   BIGINT ) * 268435456 ) 
                     AS   BINARY ( 4 )) AS   INT )
END
GO

SELECT  
    dbo.HexToINT( ' 0ABC ' ) , 
    dbo.HexToINT( ' 7FFF ' ) , 
    dbo.HexToINT( ' 0FFF ' ) , 
    dbo.HexToINT( ' 0 ' )     AS  Zero, 
    dbo.HexToINT( ' 7FFFFFFF ' )  AS  MaxValue,
    dbo.HexToINT( ' 80000000 ' )  AS  MaxNeg,
    dbo.HexToINT( ' FFFFFFFF ' )  AS  NegOne

faster dbo.ufn_vbintohexstr - varbinary to hex
http://www.sqlservercentral.com/scripts/contributions/1497.asp

create   function  dbo.ufn_vbintohexstr
(
  @vbin_in   varbinary ( 256 )
)
returns   varchar ( 514 )
as
Begin
    declare   @x   bigint
    declare   @len   int
    declare   @loop   int
    declare   @value   varbinary ( 514 )
    set   @value   =  0x
    set   @loop   =   1
    set   @len   =   datalength ( @vbin_in )
    if  ( @len   &   1 )  <>   0
       set   @vbin_in   =   0x00   +   @vbin_in
    if  ( @len   &   3 )  <   3
       set   @vbin_in   =   0x0000   +   @vbin_in
    while   @loop   <=   @len
       begin
          set   @x   =   CAST ( substring ( @vbin_in , @loop , 4 ) AS   BIGINT )
          set   @x   = 65536 *
          ( ( @x & 0xF0000000 ) * 4096
            + ( @x & 0x0F000000 ) * 256
            + ( @x & 0x00F00000 ) * 16
            + ( @x & 0x000F0000 ) )
            + ( @x & 0xF000 ) * 4096
            + ( @x & 0x0F00 ) * 256
            + ( @x & 0x00F0 ) * 16
            + ( @x & 0x000F )
          set   @x   =  ( @x   |   0x3030303030303030 ) +
             (( @x + 0x0606060606060606 ) / 16
                 &   0x0101010101010101 ) * 7
          select   @value    =   @value   +   CAST ( @x   AS   BINARY ( 8 ))
          set   @loop   =   @loop   +   4
       end
    return   ' 0x ' +   right ( CAST ( @value   AS   VARCHAR ( 514 )),  @len * 2 )
end
GO
select  dbo.ufn_vbintohexstr( 0x123456789abcdef1234 )
--  outputs: 0x0123456789ABCDEF1234
GO