instruction: tell me the top four drugs that are most frequently prescribed for patients in the 30s since 2101?
response: SELECT t1.drug FROM (SELECT prescriptions.drug, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM prescriptions WHERE prescriptions.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.age BETWEEN 30 AND 39) AND STRFTIME('%y', prescriptions.startdate) >= '2101' GROUP BY prescriptions.drug) AS t1 WHERE t1.c1 <= 4