ขอทราบจำนวนคนไข้ที่วินิจฉัยว่าน้ำหนักลดผิดปกติ และผลตรวจจากห้องปฏิบัติการเป็นเยื่อหุ้มปอดหรือไม่ ไม่จำเป็นต้องใช้ตารางทั้งหมด
give me the number of patients whose diagnoses short title is abnormal loss of weight and lab test fluid is pleural?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 INNER JOIN lab ON demographic.hadm_id = lab.hadm_id WHERE diagnoses.short_title = "Abnormal loss of weight" AND lab.fluid = "Pleural"