Which services type had successful event details?
select t1.service_type_code from services as t1 join events as t2 on t1.service_id = t2.service_id where t2.event_details = 'Success'
What about events that had failure for their event details?
select t1.service_type_code from services as t1 join events as t2 on t1.service_id = t2.service_id where t2.event_details = 'Fail'
Which service types had both success and failure for their event details?
select t1.service_type_code from services as t1 join events as t2 on t1.service_id = t2.service_id where t2.event_details = 'Success' intersect select t1.service_type_code from services as t1 join events as t2 on t1.service_id = t2.service_id where t2.event_details = 'Fail'