Re: Credit card numbers

On Sun, 07 May 2000 12:19:47 GMT, Fernando <spamers_at_must.die> wrote:

>Hi!
>
> A few questions about credit cards:
>
>a) Waht's the acceptable range for credit cards? Should I include the
>spaces between the numbers, or is it unimportant?
>
>b) Should the number be a unique key? Can two cards of diferent
>companies (say, visa and amex) have the same number?
>
I believe this is similar to the SSN# question and, while each card should be unique you can't count on it, a compound key including company would be more likely to be unique but generally I've been told it's better not to use 'real world' keys because you can't count on them to remain unique or not change. For example what if someone loses their card and the number changes, unless you provide for that you end up with a dead record and a new account with no history, when the customer should have a history. (Well *some* customers might prefer this but that's another issue)

So I believe it's held that you can do something like this but it's a bad idea and the key should be unique within the database and not a real world attribute.

I have no idea about the spaces.

hth;

DCraig. Received on Sun May 07 2000 - 00:00:00 CEST