นับจำนวนผู้ป่วยที่ได้รับน้ำเกลือปกติ 3% ไม่จำเป็นต้องใช้ทุกตาราง
count the number of patients who have been on 3% normal saline intake.It is not neccessary to use all the tables.
 procedures_icd:  row_id [ number]  subject_id [ number]  hadm_id [ number]  icd9_code [ text]  charttime [ time] 
SELECT COUNT(DISTINCT admissions.subject_id) FROM admissions WHERE admissions.hadm_id IN (SELECT icustays.hadm_id FROM icustays WHERE icustays.icustay_id IN (SELECT inputevents_cv.icustay_id FROM inputevents_cv WHERE inputevents_cv.itemid IN (SELECT d_items.itemid FROM d_items WHERE d_items.label = '3% normal saline' AND d_items.linksto = 'inputevents_cv')))