Find the names of stadiums that the least swimmers have been to?
SELECT t3.name FROM record AS t1 JOIN event AS t2 ON t1.event_id   =   t2.id JOIN stadium AS t3 ON t3.id   =   t2.stadium_id GROUP BY t2.stadium_id ORDER BY count ( * )  DESC LIMIT 1
least swimmers refers to MIN(count(swimmer_id)); names of stadiums refers to stadium.name;