CREATE TABLE t1 
(
  id number, 
  ftr_type VARCHAR2(10), 
  geom SDO_GEOMETRY
);

CREATE TABLE t2 
(
  id number, 
  ftr_type VARCHAR2(10), 
  geom SDO_GEOMETRY
);

INSERT INTO t1(id,ftr_type,geom) VALUES 
(1,
'CABLE',
MDSYS.SDO_GEOMETRY
 (
  2002,
  null,
  null,
  MDSYS.SDO_ELEM_INFO_ARRAY (1,2,1),
  MDSYS.SDO_ORDINATE_ARRAY (10,10, 20,25, 30,10, 40,10)
 )
);

INSERT INTO t1(id,ftr_type,geom) VALUES 
(2,
'F_CABLE',
MDSYS.SDO_GEOMETRY
 (
  2002,
  null,
  null,
  MDSYS.SDO_ELEM_INFO_ARRAY (1,2,1),
  MDSYS.SDO_ORDINATE_ARRAY (1,1, 2,5, 3,7, 4,8)
 )
);

/***********************************/
INSERT INTO t2(id,ftr_type,geom) VALUES 
(3,
'CABLE',
MDSYS.SDO_GEOMETRY
 (
  2002,
  null,
  null,
  MDSYS.SDO_ELEM_INFO_ARRAY (1,2,1),
  MDSYS.SDO_ORDINATE_ARRAY (1,1, 2,2)
  )
);

INSERT INTO t2(id,ftr_type,geom) VALUES 
(4,
'F_CABLE',
MDSYS.SDO_GEOMETRY
 (
  2002,
  null,
  null,
  MDSYS.SDO_ELEM_INFO_ARRAY (1,2,1),
  MDSYS.SDO_ORDINATE_ARRAY (3,3, 4,4,5,5,6,6)
 )
);

SQL> CREATE OR REPLACE VIEW CABLE
  2  AS
  3  SELECT id, ftr_type,geom FROM t1 WHERE ftr_type = 'CABLE'
  4  UNION
  5  SELECT id, ftr_type,geom FROM t2 WHERE ftr_type = 'CABLE'
  6  /
View created.

SQL> select * from cable;
select * from cable
*
ERROR at line 1:
ORA-22901: cannot compare nested table or VARRAY or LOB attributes of an object type