INSERTING VALUES INTO A NESTED TABLE - sql

Question

I am trying to develop a university database with the help of nested tables, I have successfully created all other nested tables required and inserted data as well, but while inserting data into marks table I am facing problem of inconsistent datatype.
codes:
CREATE OR REPLACE TYPE MODULE_MARKS;
CREATE OR REPLACE TYPE MM_NT_TYPE AS TABLE OF REF MODULE_MARKS;
CREATE OR REPLACE TYPE MODULE_MARKS AS OBJECT
(
MODULE REF MODULE_T, MARKS_OBTAINED, TOTAL_MARKS, STATUS
)
CREATE TABLE MARK_TAB
(
student ref student_t,
modules_marks mm_nt_type
)
I am able to insert reference to student correctly but I want to insert data into module_marks.
Tried doing :
INSERT INTO MARK_TAB VALUES((SELECT REF(S) FROM STUDENT_TAB S WHERE
S.S_ID=1),
MM_NT_TYPE( MODULE_MARKS_T((SELECT REF (M) FROM MODULE_TAB M WHERE
M.MODULE_ID =1),
90,100,'PASS')));
this shoes the error ORA-00932. EXPECTED REFERENCE OF MODULE_MARKS_T GOT MODULE_MARKS_T.

Answer 1

It seems a familiar structure to me. Maybe I have created the same structure for one of my projects.
I think you are confused when inserting the record in the column having a type which is table of REF.
I have COURSES_TABLE_TYPE which is table of REF COURSES_T and courses table is table of COURSES_T;
I suggest you do the following:
INSERT INTO DEPARTMENT VALUES (
1,
COURSES_TABLE_TYPE(( -- REFs of single records delimited by comma
SELECT
REF(C)
FROM
COURSE C
WHERE
COURSE_ID = 1
),(
SELECT
REF(C)
FROM
COURSE C
WHERE
COURSE_ID = 2
))
);

Answer 2

MM_NT_TYPE is a collection of REF MODULE_MARKS whereas you are passing MODULE_MARKS objects and not references. Instead, you need to have a table containing containing MODULE_MARKS objects that you can reference:
CREATE TABLE module_marks_tab OF module_marks;
Then you can reference those objects. For example:
INSERT INTO mark_tab VALUES (
( SELECT REF(s) FROM students s WHERE id = 2 ),
MM_NT_TYPE(
( SELECT REF( m ) FROM module_marks_tab m WHERE m.module.id = 1 AND marks_obtained = 3 ),
( SELECT REF( m ) FROM module_marks_tab m WHERE m.module.id = 3 AND marks_obtained = 8 )
)
);
db<>fiddle