Incrementing an Alpha-Numeric Number
An alpha-numeric number is a number that contains both letters and numbers.
(Example: B2XC41YD)
Why use an alpha-numeric number rather than just a regular old number I asked? The requirement for an alpha-numeric order number was written into an eCommerce spec on the project I was assigned to develop. The answer was a good one...volume. The Web site owners wanted to maintain a 4-digit order number but didn't want to be limited to 10,000 orders (0000-9999). (They were being optimistic about the store's volume.)
So I did the math. The common numbering system is Base10, meaning that any single digit could be 0-9. So a 4 digit number is 10 to the 4th power or 10,000 (0 thru 9999). An alpha-numeric number of the same length, 4 digits, would be Base36 or A-Z plus 0-9. So an alpha-numeric 4-digit number has 1.67 million possible order numbers.
There is, however, a potential problem with using an alpha-numeric order number. Namely unintended spellings like "WE8U" (We hate you), "UASS" or the numerous other four-letter words that would eventually show up. Use your imagination. The solution we settled on was to remove all vowels, A,E,I,O and U. This had the added benefit of removing the possible confusion of the letter O with zero 0.
So we will be using a Base31 alpha-numeric 4-digit number for this sample, which gives us 31 to the 4th power or just under 1 million potential order numbers (923,521 to be exact). Enough chatter, let's get into the code.
I wrote it as a function where you pass the "current" order number and get back the next order number in the sequence. You would still need to store your current "high" number somewhere.
REM Open the function and pass in the old number
function GetNextOrderNumber(Old_Number)
maxOrderID = Old_Number
Dim alphaNum
Dim alphaNumList
alphaNumList ="0,1,2,3,4,5,6,7,8,9,B,C,D,F,G,H,J,K,L,M,N,P,Q,R,S,T,V,W,X,Y,Z"
'Note that the alphaNumList does not contain the vowels.
REM Split the alphanumList into an array
alphaNum = split(alphaNumList,",")
REM Parse the current order number into an array.
Dim F(4)
F(0) = Right(Left(maxOrderID,1),1)
F(1) = Right(Left(maxOrderID,2),1)
F(2) = Right(Left(maxOrderID,3),1)
F(3) = Right(Left(maxOrderID,4),1)
REM Loop thru each position starting with the last digit.
For Y = 3 to 0 Step -1
REM If the last position is Z then roll it over to 0
If F(Y) = "Z" then
F(Y) = "0"
else
For X = 0 to 30
If F(Y) = alphaNum(X) then
NewF = alphaNum(X+1)
End If
Next
F(Y) = NewF
exit for
End if
Next
REM Rebuild the new order number from the array
newOrderID = F(0) & F(1) & F(2) & F(3)
REM Return the new order number
GetNextOrderNumber = newOrderID
end function
That's it, a simple function to convert a 4-digit number from 10,000 order numbers to just under 1 million potential order numbers. By the same logic a 6-digit number will give you 887 million potential order numbers. If we have 887 million orders in our store, I'm demanding a percentage and retiring.
Good luck and good coding.
Robin G. Grimes is currently converting sites he developed for Compaq to the new Hewlett Packard design. His favorite project is an eCommerce site that sells Compaq Spare Parts (http://sparesstore.compaq.com/sparesstore).
Based in Houston Texas, he started in database development with Stewart Title and moved to Internet development while working for Williams Communications. His current field of expertise is ASP, VBScript and Webcrossing. Webcrossing is a commercial forums language
used by Compaq, Apple, Adobe and many others. He is a frequent poster at www.webxharbor.com, where he enjoys solving problems helping others, and finding solutions to his own issues.
Robin can be reached at Robin@thegrimes.com, and welcomes all feedback on this article and related topics.
