SQL duplicates with different primary keys

Question

I have a table in this form:

id | firstname | lastname
---+-----------+----------
1  | alex      | marti
2  | mark      | finger
3  | alex      | marti
4  | ted          


        

Answer 1

select a.* from t a,
(select first, last from t group by first, last having count(*) > 1) b
where a.first = b.first and a.last = b.last