CREATE TABLE services (service_id NUMBER, service_type_code CLOB)
CREATE TABLE participants_in_events (event_id NUMBER, participant_id NUMBER)
CREATE TABLE events (event_id NUMBER, service_id NUMBER, event_details CLOB)
CREATE TABLE participants (participant_id NUMBER, participant_type_code CLOB, participant_details CLOB)

What is the id of the event with the most participants?
SELECT event_id FROM participants_in_events GROUP BY event_id ORDER BY COUNT(*) DESC LIMIT 1
SELECT "event_id" FROM "participants_in_events" GROUP BY "event_id" ORDER BY COUNT(*) DESC FETCH FIRST 1 ROWS ONLY