when patient 79919 was prescribed 0.9% sodium chloride first time in 06/last year.
select prescriptions.startdate from prescriptions where prescriptions.hadm_id in ( select admissions.hadm_id from admissions where admissions.subject_id = 79919 ) and prescriptions.drug = '0.9% sodium chloride' and datetime(prescriptions.startdate,'start of year') = datetime(current_time,'start of year','-1 year') and strftime('%m',prescriptions.startdate) = '06' order by prescriptions.startdate asc limit 1