instruction: in total, count the number of patients who have been prescribed dicloxacillin until 3 years ago.
response: SELECT COUNT(DISTINCT admissions.subject_id) FROM admissions WHERE admissions.hadm_id IN (SELECT prescriptions.hadm_id FROM prescriptions WHERE prescriptions.drug = 'dicloxacillin' AND DATETIME(prescriptions.startdate) <= DATETIME(CURRENT_TIME(), '-3 year'))