My question is similar to this one, but adds a little more complexity.
How can I flag duplicate entries in a Google Sheets column unless the duplicates have different values in another column? For instance, consider the table
col A col B -------------- abc 123 def 123 ghi 456 ghi 456
How can I flag the last two rows which are the same in both
col A and
col B but not the first two which differ in