instruction: since 5 years ago, what is the three most frequent medication prescribed during the same month to the patients aged 20s after they had been diagnosed with need prphyl vc vrl hepat?
response: SELECT t3.drug FROM (SELECT t2.drug, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM (SELECT admissions.subject_id, diagnoses_icd.charttime FROM diagnoses_icd JOIN admissions ON diagnoses_icd.hadm_id = admissions.hadm_id WHERE diagnoses_icd.icd9_code = (SELECT d_icd_diagnoses.icd9_code FROM d_icd_diagnoses WHERE d_icd_diagnoses.short_title = 'need prphyl vc vrl hepat') AND DATETIME(diagnoses_icd.charttime) >= DATETIME(CURRENT_TIME(), '-5 year')) AS t1 JOIN (SELECT admissions.subject_id, prescriptions.drug, prescriptions.startdate FROM prescriptions JOIN admissions ON prescriptions.hadm_id = admissions.hadm_id WHERE admissions.age BETWEEN 20 AND 29 AND DATETIME(prescriptions.startdate) >= DATETIME(CURRENT_TIME(), '-5 year')) AS t2 ON t1.subject_id = t2.subject_id WHERE t1.charttime < t2.startdate AND DATETIME(t1.charttime, 'start of month') = DATETIME(t2.startdate, 'start of month') GROUP BY t2.drug) AS t3 WHERE t3.c1 <= 3