มีผู้ป่วยกี่คนที่อยู่ในวอร์ด 52 จนถึงปี 2104?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
how many patients stayed on the 52 ward until 2104?It is not neccessary to use all the tables.
 icustays:  row_id [ number]  subject_id [ number]  hadm_id [ number]  icustay_id [ number]  first_careunit [ text]  last_careunit [ text]  first_wardid [ number]  last_wardid [ number]  intime [ time]  outtime [ time] 
SELECT COUNT(DISTINCT admissions.subject_id) FROM admissions WHERE admissions.hadm_id IN (SELECT transfers.hadm_id FROM transfers WHERE transfers.wardid = 52 AND STRFTIME('%y', transfers.intime) <= '2104')