Выбор ссылки на строку varray, которая находится в таблице

Question

У меня есть таблица, в которой есть столбец varray, и varray создается из пользовательского типа. Я пытаюсь получить ссылки на строки varray, но я не могу это сделать. так что это в основном таблица (столбец, столбец, столбец, столбец varray некоторого типа [объект, объект, объект]), и я пытаюсь выбрать REF (объект).

Это домашняя работа, и у меня естьчтобы завершить это, используйте REF.

DB _ ****** - это мое имя пользователя и пароль, чтобы использовать типы, которые я создаю с моего сервера uni, мне нужно использовать свое имя пользователя.typename (я не знаюпочему)

Типы и таблицы:

------ORDER------
CREATE OR REPLACE TYPE in_plant_order AS OBJECT(
    id NUMBER,
    from_warehouse REF DB_******.WAREHOUSE,
    to_warehouse REF DB_******.WAREHOUSE,
    in_plant REF DB_******.PLANT,
    createdAt DATE,
    executedAt DATE,
    --consturctor --could not figure out how to make custom constructor, it would be fantastic if you could explain me
    MEMBER PROCEDURE execute(executionDate IN DATE),
    MEMBER PROCEDURE set_from_warehouse(warehouse IN REF DB_******.WAREHOUSE),
    MEMBER PROCEDURE set_to_warehouse(warehouse IN REF DB_******.WAREHOUSE),
    MEMBER PROCEDURE set_in_plant(plant IN REF DB_******.PLANT)
);
--compiling everything does not work, but highliting them one by one and then compiling works for some reason
CREATE OR REPLACE TYPE BODY in_plant_order AS
    MEMBER PROCEDURE execute(executionDate IN DATE) IS 
    BEGIN
        self.executedAt := executionDate;
    END execute;
    MEMBER PROCEDURE set_from_warehouse(warehouse IN REF DB_******.WAREHOUSE) IS 
    BEGIN
        self.from_warehouse := warehouse;
    END set_from_warehouse;
    MEMBER PROCEDURE set_to_warehouse(warehouse IN REF DB_******.WAREHOUSE) IS 
    BEGIN
        self.from_warehouse := warehouse;
    END set_to_warehouse;
    MEMBER PROCEDURE set_in_plant(plant IN REF DB_******.PLANT) IS BEGIN
        self.in_plant := plant;
    END set_in_plant;
END;

CREATE TABLE orders OF in_plant_order(
    id PRIMARY KEY,
    from_warehouse NULL,
    to_warehouse NULL,
    in_plant NULL,
    createdAt NOT NULL,
    executedAt NULL
);

------PLANT-------
CREATE OR REPLACE TYPE warehouse_list AS VARRAY(3) of DB_******.warehouse;

 CREATE OR REPLACE TYPE plant AS OBJECT (
    id NUMBER,
    location_id NUMBER,
    size_ NUMBER(3, 2),
    size_unit_id NUMBER,
    warehouses WAREHOUSE_LIST
    -- here i need a custom constructor to check if the warehouse has the correct location id
 ); 

 CREATE TABLE plants OF plant(
    id PRIMARY KEY,
    FOREIGN KEY (location_id) REFERENCES DB_******.possible_locations_enum(id),
    location_id NOT NULL,
    FOREIGN KEY (size_unit_id) REFERENCES DB_******.size_unit_enum(id),
    size_unit_id NOT NULL
 );

----WAREHOUSE-----
 CREATE OR REPLACE TYPE warehouse AS OBJECT (
   id NUMBER,
   location_id NUMBER,
   size_ FLOAT,
   size_unit_id NUMBER,
   shelves  DB_******.shelf_list);

Процедура вставки в таблицу заказов (вот где у меня проблема):

create or replace PROCEDURE CREATE_ORDER 
(
  ORDER_ID IN NUMBER 
, WH_FROM_ID IN NUMBER 
, WH_TO_ID IN NUMBER 
, PLANT_ID IN NUMBER 
) AS 
    from_warehouse REF DB_********.warehouse;
    to_warehouse REF DB_********.warehouse;
    in_plant REF DB_********.plant;
    in_plant_order DB_********.in_plant_order;

-- For this i am getting error PL/SQL: ORA-00904: "W"."WAREHOUSE": invalid --identifier ( it does not compile )
    CURSOR c_warehouse_from IS
        SELECT REF(w.warehouse)
        FROM DB_********.plants plants, TABLE(plants.warehouses) w
        WHERE w.id = wh_from_id
          AND plants.id = plant_id;

-- This compiles but i get this error:
-- Connecting to the database FRTU.
-- ORA-22885: cannot get REF to a non-persistent object
-- ORA-06512: at "DB_******.CREATE_ORDER", line 14
-- ORA-06512: at "DB_******.CREATE_ORDER", line 33
-- ORA-06512: at line 12
-- Process exited.
-- Disconnecting from the database FRTU 
    CURSOR c_warehouse_to IS
        SELECT REF(w)
        FROM DB_********.plants plants, TABLE(plants.warehouses) w
        WHERE w.id = wh_to_id
          AND plants.id = plant_id;

    CURSOR c_plant IS
        SELECT REF(plants)
        FROM DB_********.plants plants
        WHERE plants.id = plant_id;
BEGIN
--create order
    in_plant_order := DB_********.in_plant_order(order_id, NULL, NULL, NULL, SYSDATE, NULL); 
--get warehouse_from ref
    OPEN c_warehouse_from;
    LOOP
        FETCH c_warehouse_from INTO from_warehouse;
        EXIT WHEN c_warehouse_from%NOTFOUND;
    END LOOP;
    CLOSE c_warehouse_from;
 --get warehouse_to ref
    OPEN c_warehouse_to;
    LOOP
        FETCH c_warehouse_to INTO to_warehouse;
        EXIT WHEN c_warehouse_to%NOTFOUND;
    END LOOP;
    CLOSE c_warehouse_to;
 --get plant reference
    OPEN c_plant;
    LOOP
        FETCH c_plant INTO in_plant;
        EXIT WHEN c_plant%NOTFOUND;
    END LOOP;
    CLOSE c_plant;
 --set references in order
    in_plant_order.set_from_warehouse(from_warehouse);
    in_plant_order.set_to_warehouse(to_warehouse);
    in_plant_order.set_in_plant(in_plant);
 --insert to table
    INSERT INTO DB_******.orders VALUES(in_plant_order);
END CREATE_ORDER;