คำนวณจำนวนคนไข้ทั้งหมดที่มีรหัส icd9 3950 ไม่จำเป็นต้องใช้ทุกตาราง
calculate the total number of patients who had icd9 code 3950It is not neccessary to use all the tables.
 procedures:  subject_id [ text]  hadm_id [ text]  icd9_code [ text]  short_title [ text]  long_title [ text] 
SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN procedures ON demographic.hadm_id = procedures.hadm_id WHERE procedures.icd9_code = "3950"