I said a database that tracks people could identify me using information about my birth. Not that everyone is born in a hospital or by a doctor. By your defin

I said a database that tracks people could identify me using information about my birth. Not that everyone is born in a hospital or by a doctor. By your definition there are no natural keys. But since that definition isn't useful we instead use one that is. The natural key is the identifier by which the thing is already known. https://en.wikipedia.org/wiki/Natural_key https://en.wikipedia.org/wiki/Natural_key