On 03/05/11 11:07, Greg Smith wrote:
> That doesn't mean you can't use
> them as a sort of foreign key indexing the data; it just means you can't
> make them the sole unique identifier for a particular entity, where that
> entity is a person, company, or part.
Classic case: a database here has several tables indexed by MAC address.
It's used for asset reporting and software inventory.
Problem: VMs generate random MAC addresses by default. They're not
guaranteed to be globally unique. Collisions have happened and will
probably happen again. In this case, it wasn't a big deal, but it just
goes to show that even the "obviously" globally unique isn't necessarily so.
--
Craig Ringer