CREATE TABLE participants (participant_id DECIMAL, participant_type_code TEXT, participant_details TEXT)
CREATE TABLE events (event_id DECIMAL, service_id DECIMAL, event_details TEXT)
CREATE TABLE participants_in_events (event_id DECIMAL, participant_id DECIMAL)
CREATE TABLE services (service_id DECIMAL, service_type_code TEXT)

Which service id and type has the least number of participants?
SELECT T3.service_id, T4.service_type_code FROM participants AS T1 JOIN participants_in_events AS T2 ON T1.participant_id = T2.participant_id JOIN events AS T3 ON T2.event_id = T3.event_id JOIN services AS T4 ON T3.service_id = T4.service_id GROUP BY T3.service_id ORDER BY COUNT(*) LIMIT 1
SELECT "T3"."service_id", "T4"."service_type_code" FROM "participants" AS "T1" JOIN "participants_in_events" AS "T2" ON "T1"."participant_id" = "T2"."participant_id" JOIN "events" AS "T3" ON "T2"."event_id" = "T3"."event_id" JOIN "services" AS "T4" ON "T3"."service_id" = "T4"."service_id" GROUP BY "T3"."service_id" ORDER BY COUNT(*) NULLS FIRST LIMIT 1