count the number of patients who underwent sm bowel exteriorization two or more times a year before.
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 = 'sm bowel exteriorization' ) and datetime(procedures_icd.charttime,'start of year') = datetime(current_time,'start of year','-1 year') group by admissions.subject_id ) as t1 where t1.c1 >= 2