Advice needed - merging a "travel" catalog back into the main catalog with updated photo flag/rank

I recently exported a couple folders from a lightroom catalog (a small portion of the catalog) to a new catalog to take while traveling. I wanted to review the photos and flag and rank them. I've returned now and not sure how I can merge the temp "travel" catalog back into the original catalog. No edits were made to the files, just flagging and ranking, but I would like to modify the main catalog with that information. 
Can I just import from that catalog and the flagging and ranking will be updated? No duplicate files created?

Thank you for assistance!