มีผู้ป่วยที่เสียชีวิตก่อนปี 2107 กี่ราย ไม่จำเป็นต้องใช้ตารางทั้งหมด
how many patients that died were born before 2107?It is not neccessary to use all the tables.
 lab:  subject_id [ text]  hadm_id [ text]  itemid [ text]  charttime [ text]  flag [ text]  value_unit [ text]  label [ text]  fluid [ text] 
SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic WHERE demographic.expire_flag = "0" AND demographic.dob_year < "2107"