ora_hash函数用来返回分区号，而dbms_rowid.rowid_object()函数用来返回object_id
select dbms_rowid.rowid_object(rowid) obj_id, ora_hash ( id, 31, 0) part_id ,count(*) from sales_fact_part group by dbms_rowid.rowid_object(rowid), ora_hash(id,31,0) order by 1;
原文：http://www.cnblogs.com/jenrrychen/p/4641752.html