how many patients during a year before underwent a open incis hern-grft nec after the previous percu abdominal drainage procedure within the same hospital visit?
select count( distinct t1.subject_id ) from ( select admissions.subject_id, procedures_icd.charttime, admissions.hadm_id 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 = 'percu abdominal drainage' ) and datetime(procedures_icd.charttime,'start of year') = datetime(current_time,'start of year','-1 year') ) as t1 join ( select admissions.subject_id, procedures_icd.charttime, admissions.hadm_id 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 = 'open incis hern-grft nec' ) and datetime(procedures_icd.charttime,'start of year') = datetime(current_time,'start of year','-1 year') ) as t2 on t1.subject_id = t2.subject_id where t1.charttime < t2.charttime and t1.hadm_id = t2.hadm_id