> > -----Original Message----- > > From: Tomasz Korycki [mailto:[EMAIL PROTECTED] > > Sent: 11 August 2003 05:26 > > To: [EMAIL PROTECTED] > > Subject: OT: Re: MySQL field data type for ISBN numbers > > > > > > At 21:08 2003-08-10, you wrote: > > >On Sun, Aug 10, 2003 at 05:25:05PM -0700, James Johnson wrote: > > > > > > > > I have a MySQL database for books. The ISBN field is set > > as varchar(15) and > > > > I've put a test ISBN number in of 1-1111-111-11. > > > > > >Note that ISBN numbers are a maximum of 13 characters, not 15. Ten > > >digits, three dashes. If you really want to save space, the > > last digit > > >is just a check digit and can always be determined through a > > formula on > > >the other digits, so as long as you verify every ISBN before > > you INSERT > > >it, you can save another digit. > > > > Hmmm...And how do You come up with an 'X' as the last digit, > > as many books > > on the shelves around me do? > > > I don't know which particular check digit algorithm is used for ISBNs > but the mod-11 algorithm uses the digits 0-9 and X for 10. >
If anyone is interested in calculating the check digit ... The ISBN layout is: 1: country code 2 - 3: publisher 4 - 9: book number assigned by publisher 10: check digit (if this equals 10, X is used) The algorithm uses weighted modulo 11 for calculating the check digit on an ISBN as follows: (a is the ISBN minus the check digit) Calculate the sum obtained by adding (10 * a[1]) + (9 * a[2]) + (8 * a[3]) + (7 * a[4]) + (6 * a[5]) + (5 * a[6]) + (4 * a[7]) + (3 * a[8]) + (2 * a[9]) Reduce the sum modulu 11 to obtain integer b (>=1 b <=11) The check digit is 11 - b This is an error-detecting algorithm - it won't tell you where the error is, only that there is one. -- /* All outgoing email scanned by AVG Antivirus /* Amer Neely, Softouch Information Services W: www.softouch.on.ca E: [EMAIL PROTECTED] V: 519.438.5887 Perl | PHP | MySQL | CGI programming for all data entry forms. "We make web sites work!" -- MySQL General Mailing List For list archives: http://lists.mysql.com/mysql To unsubscribe: http://lists.mysql.com/[EMAIL PROTECTED]
