Show any customer event id numbers that have corresponding notes.
select t1.customer_event_id from customer_events as t1 join customer_event_notes as t2 on t1.customer_event_id = t2.customer_event_id
How many appear have more than 5 notes?
select t1.customer_event_id from customer_events as t1 join customer_event_notes as t2 on t1.customer_event_id = t2.customer_event_id group by t1.customer_event_id having count(*) > 5
How about between 1 and 3 notes? Also show property id.
select t1.customer_event_id, t1.property_id from customer_events as t1 join customer_event_notes as t2 on t1.customer_event_id = t2.customer_event_id group by t1.customer_event_id having count(*) between 1 and 3