ผู้ป่วยรายที่ 15968 วัดค่า bp ของหลอดเลือด [ค่าล่าง] ครั้งแรกเมื่อใด?ไม่จำเป็นต้องใช้ตารางทั้งหมด
when was patient 15968 first measured a arterial bp [diastolic]?It is not neccessary to use all the tables.
 prescriptions:  row_id [ number]  subject_id [ number]  hadm_id [ number]  startdate [ time]  enddate [ time]  drug [ text]  dose_val_rx [ text]  dose_unit_rx [ text]  route [ text] 
SELECT chartevents.charttime FROM chartevents WHERE chartevents.icustay_id IN (SELECT icustays.icustay_id FROM icustays WHERE icustays.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 15968)) AND chartevents.itemid IN (SELECT d_items.itemid FROM d_items WHERE d_items.label = 'arterial bp [diastolic]' AND d_items.linksto = 'chartevents') ORDER BY chartevents.charttime LIMIT 1