SQL Server 二進制轉為十進制

CREATE FUNCTION BinaryToDec (@BinaryChar char(10))  
RETURNS int 
AS  
BEGIN 
    DECLARE @stringLength int,@ReturnValue int,@Index int
    DECLARE @CurrentChar char(1)
    SET @Index = 0
    SET @ReturnValue = 0
    SET @stringLength = LEN(@BinaryChar)
    While @Index<@stringLength
        BEGIN
            SET @Index = @Index + 1
            SET @CurrentChar = SUBSTRING(@BinaryChar,@Index,1)
            IF(@CurrentChar='1' or @CurrentChar='0')
                BEGIN
                    SET @ReturnValue = @ReturnValue + (CAST(@CurrentChar as int) * POWER(2,@stringLength - @Index))
                END
        END
    RETURN @ReturnValue
END