Oracle Solution for Error ora-12013

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

What triggered the Error:

The updatable materialized view query contained a join, subquery, union, connect by, order by, or group by caluse.

What should we do to fix it:

Make the materialized view simpler. If a join is really needed, make multiple simple materialized views then put a view on top of them.