นับจำนวนผู้ป่วยเพศ ม. ไม่จำเป็นต้องใช้ตารางทั้งหมด
count the number of patients whose gender is m?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.gender = "M"