十六進位數轉換為十進位數

CREATE FUNCTION dbo.f_hex_dec(@s varchar(16))
RETURNS bigint
AS
BEGIN
--作者：pbsql
--參數不得含'0'～'9'、'a'～'f'、'A'～'F'之外的任一字元（首尾空格除外），否則返回0
  DECLARE @i int,@result bigint
  SELECT @i=0,@result=0,@s=RTRIM(LTRIM(UPPER(REVERSE(@s))))
  WHILE @i<LEN(@s)
  BEGIN
    IF SUBSTRING(@s,@i+1,1) not between '0' and '9' and SUBSTRING(@s,@i+1,1) not between 'A' and 'F'
    BEGIN
      SELECT @result=0
      break
    END
    SELECT @result=@result+(CHARINDEX(SUBSTRING(@s,@i+1,1),'0123456789ABCDEF')-1)*POWER(16,@i),@i=@i+1
  END
  RETURN @result
END
GO