when patient 23929 was prescribed for the last time in 08/2104 iso-osmotic dextrose and insulin at the same time?
select t1.startdate from ( select admissions.subject_id, prescriptions.startdate from prescriptions join admissions on prescriptions.hadm_id = admissions.hadm_id where prescriptions.drug = 'iso-osmotic dextrose' and admissions.subject_id = 23929 and strftime('%y-%m',prescriptions.startdate) = '2104-08' ) as t1 join ( select admissions.subject_id, prescriptions.startdate from prescriptions join admissions on prescriptions.hadm_id = admissions.hadm_id where prescriptions.drug = 'insulin' and admissions.subject_id = 23929 and strftime('%y-%m',prescriptions.startdate) = '2104-08' ) as t2 on t1.subject_id = t2.subject_id where datetime(t1.startdate) = datetime(t2.startdate) order by t1.startdate desc limit 1