Oracle Message ORA-12013 - updatable materialized views must be simple enough to do fast refresh

ERRORupdatable materialized views must be simple enough to do fast refresh
CAUSEThe updatable materialized view query contained a join, subquery, union, connect by, order by, or group by caluse.
ACTIONMake the materialized view simpler. If a join is really needed, make multiple simple materialized views then put a view on top of them.