What is the description of the treatment type that costs the least money in total?
create table treatments (treatment_type_code varchar, PRIMARY KEY (treatment_type_code)); create table treatment_types (treatment_type_description varchar, treatment_type_code varchar, PRIMARY KEY (treatment_type_description))
select t1.treatment_type_description from treatment_types as t1 join treatments as t2 on t1.treatment_type_code = t2.treatment_type_code group by t1.treatment_type_code order by sum(cost_of_treatment) limit 1