about PostgreSQL...(important)

Hi to all:
    I have a question.
    PostgreSQL is Object-Relational DBMS . Can I progam Object-Oriented
Language for PostgreSQL?

Example:
    I create two tables:
                create table Address(
                              street char(20),
                              city char(20),
                              province char(20)
                 );

                 create table students(
                                 no int4,
                                 name char(8),
                                 address  Address,
                )
               insert into Address values ('ZHONG-SHAN','TAIPEI','TAIWAN');

    I find the Address record's oid:
            =>  select oid from Address where province='TAIWAN';

                               oid
                             --------
                              28672
    Then, I insert a record to students table:
            =>  insert into students values (8852,'John',28672::Address);

   Finally, I select the  record about the student's province depend on oid:
            =>select no,name,address.province from students;

   BUT PostgreSQL's message is error,why?

Thank you.....
                 Frank