Luhn algorithm

DELIMITER //
CREATE FUNCTION `LuhnCheck` (CC CHAR(19)) RETURNS BOOLEAN
BEGIN
  DECLARE i, mysum, r INT;
  DECLARE skip BOOLEAN;

  SET skip = TRUE;
  SET mysum = 0;

  SET i = CHAR_LENGTH(CC);

  WHILE i > 0 DO
    IF NOT skip THEN
      SET r = SUBSTRING(CC, i, 1) * 2;
      SET mysum = mysum + IF(r > 9, r - 9, r);
    ELSE
      SET mysum = mysum + SUBSTRING(CC, i, 1);
    END IF;

    SET i = i - 1;
    SET skip = NOT skip;
  END WHILE;

RETURN IF((MOD(mysum, 10) = 0) AND mysum <> 0, TRUE, FALSE);
END;
//
DELIMITER ;

Tuesday 10 Apr 2007 | Coding, MySQL

4 Responses to “Luhn algorithm”

1. on 10 Apr 2007 at 8:28 pm   Jay Pipes
   
   

   Hi!

   This rocks! Be sure to add it to the MySQL Forge snippet repository.

   http://forge.mysql.com/snippets/

   Cheers!

   Jay

2. on 11 Apr 2007 at 1:46 am   Dmitri Mikhailov
   
   

   Client browser, application server are the right places for this checks.

3. on 12 Apr 2007 at 8:45 am   Arjen Lentz
   
   

   You don’t want to do this. See http://arjen-lentz.livejournal.com/88612.html

4. on 13 Apr 2007 at 4:36 am   Roland Bouman
   
   

   Hi!

   I’d say, my implementation is quite near yours:

   http://rpbouman.blogspot.com/2006/12/mysql-stored-routines-and-command-line.html

   Interestingly, I put up mine as a little contest to see who could guess what it does…I never got much response, but my intention was to reprint with inline code comments. So what do you think, does such a procedure deserve some comments? And…can you find the bug in my procedure?

   kind regards,

   Roland

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