How to exclude all duplicates but one?
I have a table with many activities for each person (on another table). I want to sort those activities for each semester (3 months period). I want to have a calculation that would give me the number of semesters each person has been working. My problem is probably simple but i just can't figure out how to have a search that would find the person (unique number) and only one of each semester.
How can i eliminate all duplicates but one of each?