ผู้ป่วย 8016 ทำการทดสอบ mch ครั้งแรกในช่วงหนึ่งเดือนก่อนหน้าเมื่อใด? ไม่จำเป็นต้องใช้ตารางทั้งหมด
when did patient 8016 had a mch test the first time during a month before?It is not neccessary to use all the tables.
 outputevents:  row_id [ number]  subject_id [ number]  hadm_id [ number]  icustay_id [ number]  charttime [ time]  itemid [ number]  value [ number] 
SELECT labevents.charttime FROM labevents WHERE labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'mch') AND labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 8016) AND DATETIME(labevents.charttime, 'start of month') = DATETIME(CURRENT_TIME(), 'start of month', '-1 month') ORDER BY labevents.charttime LIMIT 1