>Hi again, Hilmar, and thanks for the reply.
>
>>Brief summary - and please note that I am no expert on this: GUID is a Windows
>>function (API) that gives you a 16-byte value, unique in the World (if the computer
>>has a network card), and very likely unique (if it doesn't).
>
>Hmmm. Sounds like IPv6 or something.

No; the MAC address (serial number of the network card) is a 48-bit value; this is incorporated into a 128-bit (16 byte) value, with this special function. It is totally unrelated to IP version 4 or 6, although the length happens to be the same as with IPv6.

>Would this be a good thing or a bad thing? (Shrug.) The larger the value, the better
>the possibility of being unique. OTOH, I'd imagine that doing something like:
>"No, Dave. The ID of that record is '_$L1B8ACF3LLJ133Z'" would be kinda obfuscated
>and cryptic when discussing this stuff over the phone :^).

The keys would used, most of the time, for internal use, IMO. Many programmers (but by no means all) agree that it is convenient to use, as the primary key, a value that is not seen by the user, thus freeing you of the need to change the primary key (and the corresponding foreign keys in other tables), when the user decides to change the coding system (client codes, city codes, whatever).