คนไข้ที่อายุน้อยกว่า 81 ปี และตรวจพบรหัส icd9 คือ 28522 มีจำนวนเท่าใด ไม่จำเป็นต้องใช้ทุกตาราง
what is the number of patients whose age is less than 81 and diagnoses icd9 code is 28522?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 diagnoses ON demographic.hadm_id = diagnoses.hadm_id WHERE demographic.age < "81" AND diagnoses.icd9_code = "28522"