instruction: how much insulin had been prescribed to patient 3929 in total this month?
response: SELECT SUM(prescriptions.dose_val_rx) FROM prescriptions WHERE prescriptions.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 3929) AND prescriptions.drug = 'insulin' AND DATETIME(prescriptions.startdate, 'start of month') = DATETIME(CURRENT_TIME(), 'start of month', '-0 month')