Refresh of large and constantly updating data

Hi,

I have very large table of around 600 M rows. It has maily two columns file names and last used date of the file. so it is constantly updated with new date and other values. using direct query is making my report slow so I want to go with import mode.

I am stuck at how do I refresh this data daily. I can't refresh all 600M rows everyday that would not be efficient. I have read about detect data changes option but I do not have two date columns for that, I only have one date column that is " Last date used " that changes constantly. so can't go with detect data changes option.

can I get a way through this ? 

Thanks !