มองหาจำนวนผู้ป่วยหญิงที่อายุต่ำกว่า 70 ปี ไม่จำเป็นต้องใช้ทุกโต๊ะ
look for the number of female patients who are less than 70 years of age.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 = "F" AND demographic.age < "70"