when were patient 20332 first prescribed for aspirin and potassium chl 20 meq / 1000 ml d5 1/2 ns 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 = 'aspirin' and admissions.subject_id = 20332 ) as t1 join ( select admissions.subject_id, prescriptions.startdate from prescriptions join admissions on prescriptions.hadm_id = admissions.hadm_id where prescriptions.drug = 'potassium chl 20 meq / 1000 ml d5 1/2 ns' and admissions.subject_id = 20332 ) as t2 on t1.subject_id = t2.subject_id where datetime(t1.startdate) = datetime(t2.startdate) order by t1.startdate asc limit 1