I would like to go into my reasoning for deliberately focussing on an ID. Yes you can just remove duplicates by Group by or SELECT DISTINCT.
In a lot of cases you have something like customer IDs or phone numbers. With DISTINCT what would happen in such a case
phone_no | adress | joined
555-1234 | main street 1 | 2008
555-1234 | main street 1C | 2009
555-1234 | Main Street 1 | 2008
you would still end up with 3 distinct cases and you would call/mail the customer three times, and what if your data is 99% unique after the ID but there are a few lines you are missing and would not see in a sample or by just looking at them.
Of course it depends on your use case in the end 