มีคนไข้กี่คนที่หย่าร้างและเป็นเชื้อชาติผิวสี/เฮติ?ไม่จำเป็นต้องใช้ตารางทั้งหมด
how many patients are divorced and are of black/haitian ethinicity?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.marital_status = "DIVORCED" AND demographic.ethnicity = "BLACK/HAITIAN"