Here's a hack :-)
Add a GROUP BY and a COUNT
SQL> create table demo_emps (
2 id number primary key,
3 name varchar2(255),
4 sal number
5 );
Table created.
SQL>
SQL> insert into demo_emps values(1, 'martin', 100);
1 row created.
SQL>
SQL> create materialized view log on demo_emps
2 with rowid, sequence, commit scn, primary key (sal)
3 including new values;
Materialized view log created.
SQL>
SQL> create materialized view demo_emps_mv
2 refresh fast on commit
3 as
4 select 1 grp, max(sal) max_sal, count(*) c
5 from demo_emps
6 group by 1
7 ;
Materialized view created.
SQL>
SQL> select *
2 from demo_emps_mv
3 ;
GRP MAX_SAL C
---------- ---------- ----------
1 100 1
SQL>
SQL> insert into demo_emps values(2, 'sally', 200);
1 row created.
SQL>
SQL> commit;
Commit complete.
SQL>
SQL> select *
2 from demo_emps_mv
3 ;
GRP MAX_SAL C
---------- ---------- ----------
1 200 2
SQL>
SQL> select staleness
2 from user_mviews
3 where 1=1
4 and mview_name = 'DEMO_EMPS_MV'
5 ;
STALENESS
-------------------
FRESH
SQL>
SQL> update demo_emps
2 set sal = sal + 1
3 ;
2 rows updated.
SQL>
SQL> commit;
Commit complete.
SQL>
SQL> select *
2 from demo_emps_mv
3 ;
GRP MAX_SAL C
---------- ---------- ----------
1 201 2
SQL>
SQL> select staleness
2 from user_mviews
3 where 1=1
4 and mview_name = 'DEMO_EMPS_MV'
5 ;
STALENESS
-------------------
FRESH
SQL>
SQL>