SQL> 
SQL> /*
DOC>
DOC>Building an MV on top of an existing table.
DOC>
DOC>*/
SQL> 
SQL> drop table t2_a;

Table dropped.

SQL> drop materialized view t2_a_mv;

Materialized view dropped.

SQL> drop table t2_a_mv;

Table dropped.

SQL> 
SQL> create table t2_a as select * from test2 nologging;

Table created.

SQL> alter table t2_a add constraint t2_a_pk primary key (c1);

Table altered.

SQL> create table t2_a_mv as select * from t2_a nologging;

Table created.

SQL> 
SQL> create materialized view t2_a_mv
  2  on prebuilt table
  3  refresh complete on demand
  4  as select * from t2_a;

Materialized view created.

SQL> 
SQL> drop materialized view t2_a_mv;

Materialized view dropped.

SQL> alter table t2_a add (newcol number);

Table altered.

SQL> alter table t2_a_mv add (newcol number);

Table altered.

SQL> 
SQL> create materialized view t2_a_mv
  2  on prebuilt table
  3  refresh complete on demand
  4  as select * from t2_a;

Materialized view created.

SQL> 
SQL> drop table t2_a;

Table dropped.

SQL> drop materialized view t2_a_mv;

Materialized view dropped.

SQL> drop table t2_a_mv;

Table dropped.

SQL> 
SQL> spool off