Using a sequential transaction counter maybe, whose values only increase in time?
For an incremental load to work, some field or set of fields should indicate new or changed records. Usually this is a Creation Date or Last Modification Date field as that is the easiest way to pull the required rows from a possibly very large table.
If you cannot find them (either in the same table or in another table that logs changes for example), you won't be able to incrementally load your table.
