I need to merge two data frames fuzzily on a Starttime_ms column. The data to be merged however have internal structure, i.e. groupings. They should be merged by the grouping variable File. How can this be done? Using fuzzyjoins function difference_left_join this does not seem possible: in row #13, the Quote “this is how” should not be assigned as the Files in df1 and df2 are different: