Table schema:
CREATE TABLE Treatments (treatment_type_code VARCHAR); CREATE TABLE Treatment_types (treatment_type_description VARCHAR, treatment_type_code VARCHAR)

Question: What is the description of the treatment type that costs the least money in total?
SQL: 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