How many participants are there?
select count ( * ) from participants
How about the total number of events?
select count ( distinct event_id ) from participants_in_events
Can you list the events that have participents whose details had the substring 'Dr.'?
select t2.event_id from participants as t1 join participants_in_events as t2 on t1.participant_id = t2.participant_id where t1.participant_details like '%dr.%'
Can you please list all those events with their participants' names?
select t2.event_id, t1.participant_details from participants as t1 join participants_in_events as t2 on t1.participant_id = t2.participant_id