Recently I read a book on relational database, which says that relations (i.e. tables of databases) are sets in principle, which means there are no intrinsic order. There are nothing like natural sort. This means that you should supply your own criteria to order / sort, as far as I understand.
Well this is rather philosophical approach and many databases provide orders through many ways, e.g. auto-created keys, but the book says that such keys are not the intrinsic part of relational database concepts.