How many events had participants whose details had the substring 'Dr.'
create table participants (participant_id varchar, participant_details varchar, PRIMARY KEY (participant_id)); create table participants_in_events (participant_id varchar, PRIMARY KEY (participant_id))
select count(*) from participants as t1 join participants_in_events as t2 on t1.participant_id = t2.participant_id where t1.participant_details like '%dr.%'