จนถึง 1 ปีที่แล้วมีผู้ป่วยกี่รายที่ได้รับการตรวจช่องไขสันหลังสองครั้ง?ไม่จำเป็นต้องใช้ตารางทั้งหมด
how many patients until 1 year ago have received spinal canal explor nec two times?It is not neccessary to use all the tables.
 d_labitems:  row_id [ number]  itemid [ number]  label [ text] 
SELECT COUNT(DISTINCT t1.subject_id) FROM (SELECT admissions.subject_id, COUNT(*) AS c1 FROM procedures_icd JOIN admissions ON procedures_icd.hadm_id = admissions.hadm_id WHERE procedures_icd.icd9_code = (SELECT d_icd_procedures.icd9_code FROM d_icd_procedures WHERE d_icd_procedures.short_title = 'spinal canal explor nec') AND DATETIME(procedures_icd.charttime) <= DATETIME(CURRENT_TIME(), '-1 year') GROUP BY admissions.subject_id) AS t1 WHERE t1.c1 = 2