ได้จำนวนผู้ป่วยรายการตรวจทางห้องปฏิบัติการ รหัส 51439 ที่เข้ารับการรักษาในโรงพยาบาลก่อนปี 2111 ไม่จำเป็นต้องใช้ตารางทั้งหมด
get the number of patients with lab test item id 51439 who were admitted to hospital before 2111.It is not neccessary to use all the tables.
 demographic:  subject_id [ text]  hadm_id [ text]  name [ text]  marital_status [ text]  age [ text]  dob [ text]  gender [ text]  language [ text]  religion [ text]  admission_type [ text]  days_stay [ text]  insurance [ text]  ethnicity [ text]  expire_flag [ text]  admission_location [ text]  discharge_location [ text]  diagnosis [ text]  dod [ text]  dob_year [ text]  dod_year [ text]  admittime [ text]  dischtime [ text]  admityear [ text] 
SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE demographic.admityear < "2111" AND lab.itemid = "51439"