SELECT count(*) FROM EVENTS WHERE event_id NOT IN (SELECT event_id FROM Participants_in_Events)
How many events did not have any participants?
SELECT count ( * ) FROM EVENTS WHERE event_id NOT IN ( SELECT event_id FROM Participants_in_Events )
select count ( * ) from events where event_id not in ( select event_id from participants_in_events )
How many events did not have any participants ?