ให้ระบุจำนวนผู้ป่วยที่เสียชีวิตและมีอายุต่ำกว่า 64 ปี ไม่จำเป็นต้องใช้ตารางทั้งหมด
Give the number of patients who died and were aged below 64 years.It is not neccessary to use all the tables.
 prescriptions:  subject_id [ text]  hadm_id [ text]  icustay_id [ text]  drug_type [ text]  drug [ text]  formulary_drug_cd [ text]  route [ text]  drug_dose [ text] 
SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic WHERE demographic.expire_flag = "1" AND demographic.age < "64"