คำนวณจำนวนผู้ป่วยที่ผ่าคออย่างรุนแรงข้างเดียวไม่จำเป็นต้องใช้ตารางทั้งหมด
calculate the total number of patients who had radical neck dissection, unilateralIt 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 INNER JOIN procedures ON demographic.hadm_id = procedures.hadm_id WHERE procedures.long_title = "Radical neck dissection, unilateral"