เข้ารับการรักษากี่คน?ไม่จำเป็นต้องใช้ตารางทั้งหมด
how many patients were admitted?It is not neccessary to use all the tables.
 transfers:  row_id [ number]  subject_id [ number]  hadm_id [ number]  icustay_id [ number]  eventtype [ text]  careunit [ text]  wardid [ number]  intime [ time]  outtime [ time] 
SELECT COUNT(DISTINCT admissions.subject_id) FROM admissions WHERE admissions.dischtime IS NULL