เมื่อผู้ป่วย 18841 ปีที่แล้วได้รับหัตถการครั้งแรก?ไม่จำเป็นต้องใช้ตารางทั้งหมด
when patient 18841 the last year first received a procedure?It is not neccessary to use all the tables.
 procedures_icd:  row_id [ number]  subject_id [ number]  hadm_id [ number]  icd9_code [ text]  charttime [ time] 
SELECT procedures_icd.charttime FROM procedures_icd WHERE procedures_icd.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 18841) AND DATETIME(procedures_icd.charttime, 'start of year') = DATETIME(CURRENT_TIME(), 'start of year', '-1 year') ORDER BY procedures_icd.charttime LIMIT 1