instruction: count the number of times patient 15209 had had a gastric tube output in 09/2105.
response: SELECT COUNT(*) FROM outputevents WHERE outputevents.icustay_id IN (SELECT icustays.icustay_id FROM icustays WHERE icustays.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 15209)) AND outputevents.itemid IN (SELECT d_items.itemid FROM d_items WHERE d_items.label = 'gastric tube' AND d_items.linksto = 'outputevents') AND STRFTIME('%y-%m', outputevents.charttime) = '2105-09'