instruction: count the number of patients who had received a feeding tube - nasogastric procedure since 2 years ago two times.
response: SELECT COUNT(DISTINCT t1.uniquepid) FROM (SELECT patient.uniquepid, COUNT(*) AS c1 FROM patient WHERE patient.patientunitstayid = (SELECT treatment.patientunitstayid FROM treatment WHERE treatment.treatmentname = 'feeding tube - nasogastric' AND DATETIME(treatment.treatmenttime) >= DATETIME(CURRENT_TIME(), '-2 year')) GROUP BY patient.uniquepid) AS t1 WHERE t1.c1 = 2