Data Refresh from Source

Hello,

I'm trying to find out more about data refresh functions.

Is there a way to get data from a source, and be sure that when a refresh takes place that only additions to the data and any changes to existing data are refreshed - without reloading existing data.

eg. If I have 100000 rows of data and 2000 rows are added with 1000 minor changes to the original 100000 rows; how would I be sure only the 2000 rows are added and the amendments loaded from a refresh without the original 100000 needing to be processed again?

Asking this with system efficiency and processing times in mind.