instruction: what is the number of patients whose admission location is clinic referral/premature and primary disease is sigmoid diverticulitis, colovestical fistula/sda?
response: SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic WHERE demographic.admission_location = "CLINIC REFERRAL/PREMATURE" AND demographic.diagnosis = "SIGMOID DIVERTICULITIS, COLOVESTICAL FISTULA/SDA"