instruction: since 5 years ago, what are the top three most frequently prescribed drugs for patients in the 50s?
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 50 AND 59) AND DATETIME(prescriptions.startdate) >= DATETIME(CURRENT_TIME(), '-5 year') GROUP BY prescriptions.drug) AS t1 WHERE t1.c1 <= 3