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