One advantage of hash index over Single table join index is that you can define "order by values (column_name)" in the hash index definition where "column_name" is defined in the "by" clause (i.e. primary index for hash index). It will make sure that rows are sequenced based upon the "values" rather than "hash" of the column_name. This feature is not available in single table join index where you cannot have an "order by" clause on the primary index defined (surely you can have any order by on any other column. default is order by hash of primary index). this difference is subtle.