หาอายุขั้นต่ำของผู้ป่วยหญิงผิวขาว ไม่จำเป็นต้องใช้ทุกโต๊ะ
find the minimum age of white female patients .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 MIN(demographic.age) FROM demographic WHERE demographic.gender = "F" AND demographic.ethnicity = "WHITE"