SQL>
SQL> create table I1(n number primary key, v varchar2(10));
SQL> create table I2(n number primary key, v varchar2(10));
SQL>
SQL> create table MAP
2 (n number primary key,
3 i1 number referencing I1(n),
4 i2 number referencing I2(n));
SQL>
SQL> create unique index IDX_MAP on MAP(i1, i2);
SQL>
SQL> insert into i1
2 select rownum, rpad('*',10,'*') from all_objects;
12651 rows created.
SQL>
SQL> insert into i2
2 select rownum, rpad('*',10,'*') from all_objects;
12651 rows created.
SQL>
SQL> insert into map
2 select rownum, rownum, rownum from all_objects;
12651 rows created.
SQL>
SQL> select *
2 from i1, map, i2
3 where i1.n = map.i1
4 and i2.n = map.i2
5 and i1.v = 'x'
6 and i2.v = 'y';
no rows selected
SQL>
SQL> drop table i1 cascade constraint;
Table dropped.
SQL> drop table map cascade constraint;
Table dropped.
SQL> drop table i2 cascade constraint;
Table dropped.