instruction: what was the four most often given procedures for patients 40s?
response: SELECT t1.treatmentname FROM (SELECT treatment.treatmentname, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM treatment WHERE treatment.patientunitstayid IN (SELECT patient.patientunitstayid FROM patient WHERE patient.age BETWEEN 40 AND 49) GROUP BY treatment.treatmentname) AS t1 WHERE t1.c1 <= 4