แสดงจำนวนผู้ป่วยที่วินิจฉัยรหัส icd9 จำนวน 4846 ราย เข้ารับการรักษาในโรงพยาบาลนานกว่า 15 วัน ไม่จำเป็นที่จะต้องใช้ตารางทั้งหมด
show me the number of patients with a diagnoses icd9 code of 4846 who were hospitalized for more than 15 days.It is not neccessary to use all the tables.
 demographic:  subject_id [ text]  hadm_id [ text]  name [ text]  marital_status [ text]  age [ text]  dob [ text]  gender [ text]  language [ text]  religion [ text]  admission_type [ text]  days_stay [ text]  insurance [ text]  ethnicity [ text]  expire_flag [ text]  admission_location [ text]  discharge_location [ text]  diagnosis [ text]  dod [ text]  dob_year [ text]  dod_year [ text]  admittime [ text]  dischtime [ text]  admityear [ text] 
SELECT COUNT(DISTINCT demographic.subject_id) FROM demographic INNER JOIN diagnoses ON demographic.hadm_id = diagnoses.hadm_id WHERE demographic.days_stay > "15" AND diagnoses.icd9_code = "4846"