นับจำนวนผู้ป่วยที่อายุน้อยกว่า 30 ปี และผลแล็บตรวจสถานะผิดปกติเป็นเดลต้าหรือไม่ ไม่จำเป็นต้องใช้ทุกตาราง
count the number of patients whose age is less than 30 and lab test abnormal status is delta?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 lab ON demographic.hadm_id = lab.hadm_id WHERE demographic.age < "30" AND lab.flag = "delta"