CREATE TABLE swimmer (id NUMBER, name CLOB, nationality CLOB, meter_100 NUMBER, meter_200 CLOB, meter_300 CLOB, meter_400 CLOB, meter_500 CLOB, meter_600 CLOB, meter_700 CLOB, time CLOB)
CREATE TABLE record (id NUMBER, result CLOB, swimmer_id NUMBER, event_id NUMBER)
CREATE TABLE event (id NUMBER, name CLOB, stadium_id NUMBER, year CLOB)
CREATE TABLE stadium (id NUMBER, name CLOB, capacity NUMBER, city CLOB, country CLOB, opening_year NUMBER)

Find the country that has the most stadiums.
SELECT country FROM stadium GROUP BY country ORDER BY COUNT(*) DESC LIMIT 1
SELECT "country" FROM "stadium" GROUP BY "country" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY