Views for every subtype on object table

Question

Hi!
The environment is (Oracle 10.2.0.3):drop type tp;
create or replace type tp as object (
  n number
) not final;
drop type tp1;
create or replace type tp1 under tp (
  n1 number
) not final;
drop type tp2;
create or replace type tp2 under tp (
  n2 number
create or replace type tp11 under tp1 (
  n11 number
create table tt of tp;
insert into tt values (tp(1));
insert into tt values (tp1(1,1));
insert into tt values (tp1(1,2));
insert into tt values (tp11(1,1,1));
insert into tt values (tp11(1,1,2));
insert into tt values (tp11(1,1,3));
commit;I'd like to create a views on table tt that will filter objects of only one of tp 's subtypes. For example:
create or replace view tp1_v as
select * from tt t where value(t) is of (only tp1);However the SELECT statement in this view get the result:SQL> select * from tt t where value(t) is of (only tp1);
    N
    1
    1
2 rows selectedThe column N1 is missing. So I try:select treat(value(t) as tp1) as "treat" from tt t where value(t) is of (only tp1);
treat
SCH.TP1(1,1)
SCH.TP1(1,2)
2 rows selectedbut I wants the output be:    N    N1
    1     1
    1     2
2 rows selectedThat SELECT will give me such output?

Answer 1

Check this
select n,treat(value(t) as tp1).n1 n1 from tt t where value(t) is of (only tp1);
N                      N1                    
1                      1                     
1                      2