instruction: what were the three most commonly given procedures for patients who had previously received a oxygen therapy (> 60%) - face mask within the same month, since 6 years ago?
response: SELECT t3.treatmentname FROM (SELECT t2.treatmentname, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM (SELECT patient.uniquepid, treatment.treatmenttime FROM treatment JOIN patient ON treatment.patientunitstayid = patient.patientunitstayid WHERE treatment.treatmentname = 'oxygen therapy (> 60%) - face mask' AND DATETIME(treatment.treatmenttime) >= DATETIME(CURRENT_TIME(), '-6 year')) AS t1 JOIN (SELECT patient.uniquepid, treatment.treatmentname, treatment.treatmenttime FROM treatment JOIN patient ON treatment.patientunitstayid = patient.patientunitstayid WHERE DATETIME(treatment.treatmenttime) >= DATETIME(CURRENT_TIME(), '-6 year')) AS t2 ON t1.uniquepid = t2.uniquepid WHERE t1.treatmenttime < t2.treatmenttime AND DATETIME(t1.treatmenttime, 'start of month') = DATETIME(t2.treatmenttime, 'start of month') GROUP BY t2.treatmentname) AS t3 WHERE t3.c1 <= 3