What is the description of the type of service that is performed the most often?
select t1.service_type_description from ref_service_types as t1 join services as t2 on t1.service_type_code = t2.service_type_code group by t1.service_type_code order by count ( * ) desc limit 1
What is the code of the type of service that is performed the most often?
select t1.service_type_code from ref_service_types as t1 join services as t2 on t1.service_type_code = t2.service_type_code group by t1.service_type_code order by count ( * ) desc limit 1
What is its parent service type code?
select t1.parent_service_type_code from ref_service_types as t1 join services as t2 on t1.service_type_code = t2.service_type_code group by t1.service_type_code order by count ( * ) desc limit 1