instruction: what were the four most frequently prescribed drugs within the same hospital visit to the patients of age 50s after having been diagnosed with pneumonia - hospital acquired (not ventilator-associated)?
response: SELECT t3.drugname FROM (SELECT t2.drugname, DENSE_RANK() OVER (ORDER BY COUNT(*) DESC) AS c1 FROM (SELECT patient.uniquepid, diagnosis.diagnosistime, patient.patienthealthsystemstayid FROM diagnosis JOIN patient ON diagnosis.patientunitstayid = patient.patientunitstayid WHERE diagnosis.diagnosisname = 'pneumonia - hospital acquired (not ventilator-associated)') AS t1 JOIN (SELECT patient.uniquepid, medication.drugname, medication.drugstarttime, patient.patienthealthsystemstayid FROM medication JOIN patient ON medication.patientunitstayid = patient.patientunitstayid WHERE patient.age BETWEEN 50 AND 59) AS t2 ON t1.uniquepid = t2.uniquepid WHERE t1.diagnosistime < t2.drugstarttime AND t1.patienthealthsystemstayid = t2.patienthealthsystemstayid GROUP BY t2.drugname) AS t3 WHERE t3.c1 <= 4