ตั้งแต่วันที่ 12/2104 ค่าต่ำสุดรายวันของ pt ของผู้ป่วย 31854 คือเท่าใด? ไม่จำเป็นต้องใช้ตารางทั้งหมด
since 12/2104, what was the daily minimum value of the pt of patient 31854?It is not neccessary to use all the tables.
 labevents:  row_id [ number]  subject_id [ number]  hadm_id [ number]  itemid [ number]  charttime [ time]  valuenum [ number]  valueuom [ text] 
SELECT MIN(labevents.valuenum) FROM labevents WHERE labevents.hadm_id IN (SELECT admissions.hadm_id FROM admissions WHERE admissions.subject_id = 31854) AND labevents.itemid IN (SELECT d_labitems.itemid FROM d_labitems WHERE d_labitems.label = 'pt') AND STRFTIME('%y-%m', labevents.charttime) >= '2104-12' GROUP BY STRFTIME('%y-%m-%d', labevents.charttime)