How many students are playing multiple sports?
select count ( * ) from ( select * from sportsinfo group by stuid having count ( * ) > 1 )
What are the names of the two students who are playing multiple sports?
select t2.fname, t2.lname from sportsinfo as t1 join student as t2 on t1.stuid = t2.stuid group by t1.stuid having count ( * ) >1