มีผู้ป่วยพักอยู่ในวอร์ด 57 กี่คน?ไม่จำเป็นต้องใช้โต๊ะทั้งหมด
how many patients had been staying in ward 57?It is not neccessary to use all the tables.
 inputevents_cv:  row_id [ number]  subject_id [ number]  hadm_id [ number]  icustay_id [ number]  charttime [ time]  itemid [ number]  amount [ number] 
SELECT COUNT(DISTINCT admissions.subject_id) FROM admissions WHERE admissions.hadm_id IN (SELECT transfers.hadm_id FROM transfers WHERE transfers.wardid = 57)