คนไข้ชายมีประกันสุขภาพเอกชนกี่คน ไม่จำเป็นต้องใช้ทุกตาราง
how many male patients have private health insurance?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.gender = "M" AND demographic.insurance = "Private"