CREATE TABLE participants (Participant_ID VARCHAR)
CREATE TABLE EVENTS (service_id VARCHAR, Event_ID VARCHAR)
CREATE TABLE services (Service_Type_Code VARCHAR, service_id VARCHAR)
CREATE TABLE Participants_in_Events (Participant_ID VARCHAR, Event_ID VARCHAR)

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