[ORA-22905] How to read a field of an object inside another object?

Question

Greetings,
I'm a student and in a current exercise we have to work with the Object Oriented Programming functionality of Oracle.
In the database we defined an object type, which is then considered inside another object type. The thing is, that I cannot read an attribute of the inner object. I've read tens of websites but none of them have helped so far. I've read the PL/SQL User Guide and Reference document also.
The inner object is defined as follows:
create type address_t as object (
        street varchar(50),
        city varchar(50),
        pcode number(5,0)
        );The outer object has an object of type address_t inside it:
CREATE TYPE professor_t as OBJECT(
          code number(2),
          p_name varchar(50),
          address address_t,
          );Also, there is a table named PROFESSORS that stores objects of type professor_t
First of all, with a simple testing SQL statement I can see the data inside the object professor, even the object address_t:
SELECT * FROM PROFESSORS WHERE CODE = 13;returns the following:
CODE    |         NAME      |       ADDRESS
13      |         JOHN     |       MYSCHEMA.ADDRESS_T('FIFTH AVENUE','NEW YORK',12345)The thing is, I want to read the field street of the object address (of type address_t) inside professor (of type professor_t).
I could see everywhere that the way to go is to use point notation, and I've seen examples about the command VALUE, but none of the following SQL statements work:
SELECT VALUE(ADDRESS.STREET) FROM(
  SELECT CODE,P_NAME,ADDRESS FROM PROFESSORS WHERE CODE = 13);
SELECT ADDRESS.STREET FROM PROFESSORS WHERE CODE = 13;
SELECT PROFESSOR.ADDRESS.STREET FROM PROFESSORS WHERE CODE = 13;I'd really appreciate if someone could show me how to access the values of the field of the object inside an object.
Thanks in advance,
- David
Edited by: 858176 on May 11, 2011 6:53 PM Formatting

Answer 1

Great, this worked so far.
It is curious that you wrote 'profesores' but that is the actual name for the variable. I translated everything to english in order to post it here.
So, the statement is:
select value(t).DIRECCION.CIUDAD from profesores t;And It returned:
VALUE(T).DIRECCION.CIUDAD                         
Valencia                                          
New York
TijuanaAnd, applying the VALUE command to the statement:
select codigo,
nombre,
value(t).DIRECCION.CALLE,
value(t).DIRECCION.CIUDAD,
value(t).DIRECCION.CP
from profesores T WHERE T.CODIGO = 13;Resulting in:
CODIGO                 NOMBRE                                             VALUE(T).DIRECCION.CALLE                           VALUE(T).DIRECCION.CIUDAD                          VALUE(T).DIRECCION.CP 
13                     Pepito Pérez                                       Calle de los Rosales 0                           Valencia                                           46023                  That is EXACTLY what I needed.
Thanks Thomas, It was really helpful !
Edited by: 858176 on May 11, 2011 7:46 PM