instruction: during the last hospital visit, what was the minimum rdw value for patient 86792?
response: SELECT MIN(labevents.valuenum) FROM labevents WHERE labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 86792 AND NOT admissions.dischtime IS NULL ORDER BY admissions.admittime DESC LIMIT 1) AND labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'rdw')