ISBN Algorithms

Here is how you get the check digit for ISBN.CREATE FUNCTION dbo.fnGetISBN
(
@ISBN VARCHAR(11)
)
RETURNS VARCHAR(13)
AS
BEGIN
DECLARE@Index TINYINT,
@Weight TINYINT,
@Sum SMALLINT

SELECT@Index = LEN(@ISBN),
@Weight = 2,
@Sum = 0

WHILE @Index > 0
BEGIN
IF SUBSTRING(@ISBN, @Index, 1) <> '-'
SELECT@Sum = @Sum + @Weight * CAST(SUBSTRING(@ISBN, @Index, 1) AS TINYINT),
@Weight = @Weight + 1

SET @Index = @Index - 1
END

RETURNCASE @Sum % 11
WHEN 1 THEN @ISBN + '-X'
ELSE @ISBN + '-' + CONVERT(CHAR(1), 11 - (@Sum % 11))
END
END
E 12°55'05.25"
N 56°04'39.16"