How to write a procedure to retrieve data in a collection from a table?

Question

create or replace type Subject as object(
subject_id number,
subject_Desc varchar2(50)
create or replace type Subjects_All as varray(10) of Subject
create table student(
StudentID varchar(10),
Subjects Subjects_all
so how do i write a procedure to display info such as this:
Subjects:
101 'Maths'
102 'Science'
Subjects:
I wrote a procedure like the following but it didn't quite work :(
CREATE OR REPLACE PROCEDURE StudentLoop AS
all_subj subjects_all;
each_subj subject;
CURSOR all_subjectsrow IS select * from student;
BEGIN
FOR all_subj IN all_subjectsrow LOOP
FOR each_subj IN all_subj LOOP
DBMS_OUTPUT.PUT_LINE('Last row selected has ID ' || each_subj.subject_id || each_subj.subject_desc );
END LOOP;
END LOOP;
END StudentLoop ;
Any Advice?

Answer 1

Hello,
1.) Don't store Types in Tables. It will become a nightmare when you want to query your data any other way then retrieving your object types. Just don't do it.
2.) A more relational model is much easier. Considering students and subjects is a n:n relation (a student can have more subjects and a subject can have more students) this might look like this:
SQL> r
  1  declare
  2    cursor cStudents is
  3      with student as (
  4        select 1 student_id, 'test1' name from dual
  5        union all
  6        select 2 student_id, 'test2' name from dual
  7      ),
  8      subjects as (
  9        select 1 subject_id, 'Maths' subject_desc from dual
10        union all
11        select 2 subject_id, 'Science' subject_desc from dual
12      ),
13      student_subjects as (
14        select 1 student_id, 1 subject_id from dual
15        union all
16        select 1 student_id, 2 subject_id from dual
17        union all
18        select 2 student_id, 2 subject_id from dual
19      )
20      select a.name name, b.subject_desc subject
21      from student a, subjects b, student_subjects c
22      where a.student_id = c.student_id
23      and b.subject_id = c.subject_id;
24  begin
25    for rS in cStudents loop
26      dbms_output.put_line('Student '||rS.name||': '||rS.subject);
27    end loop;
28* end;
Student test1: Maths
Student test2: Science
Student test1: Sciencecheers