Oracle PL/SQL - INSTEAD OF-Triggerbeispiel

CREATE TABLE customer_details
(
    customer_id number(10) primary key,
    customer_name varchar2(20),
    country varchar2(20)
);

CREATE TABLE projects_details
(
    project_id number(10) primary key,
    project_name varchar2(30),
    project_start_Date date,
    customer_id number(10) references customer_details(customer_id)
);

CREATE OR REPLACE VIEW customer_projects_view AS
   SELECT cust.customer_id, cust.customer_name, cust.country,
          projectdtls.project_id, projectdtls.project_name,
          projectdtls.project_start_Date
   FROM customer_details cust, projects_details projectdtls
   WHERE cust.customer_id = projectdtls.customer_id;

INSERT INTO customer_projects_view VALUES (1,'XYZ Enterprise','Japan',101,'Library management',sysdate);

-- output
SQL Error: ORA-01779: cannot modify a column which maps to a non key-preserved table
01779. 00000 -  "cannot modify a column which maps to a non key-preserved table"
*Cause:    An attempt was made to insert or update columns of a join view which
           map to a non-key-preserved table.
*Action:   Modify the underlying base tables directly.

CREATE OR REPLACE TRIGGER trg_cust_proj_view_insert
   INSTEAD OF INSERT ON customer_projects_view
   DECLARE
     duplicate_info EXCEPTION;
     PRAGMA EXCEPTION_INIT (duplicate_info, -00001);
   BEGIN

   INSERT INTO customer_details
       (customer_id,customer_name,country)
     VALUES (:new.customer_id, :new.customer_name, :new.country);

   INSERT INTO projects_details (project_id, project_name, project_start_Date, customer_id)
   VALUES (
     :new.project_id,
     :new.project_name,
     :new.project_start_Date,
     :new.customer_id);

   EXCEPTION
     WHEN duplicate_info THEN
       RAISE_APPLICATION_ERROR (
         num=> -20107,
         msg=> 'Duplicate customer or project id');
   END trg_cust_proj_view_insert;

INSERT INTO customer_projects_view VALUES (1,'XYZ Enterprise','Japan',101,'Library management',sysdate);

INSERT INTO customer_projects_view VALUES (2,'ABC Infotech','India',202,'HR management',sysdate);

SELECT * FROM customer_details;

SELECT * FROM projects_details;

SELECT * FROM customer_projects_view;

CREATE TABLE vehicle_mfg_company_details (
  company_id number(10) primary key,
  company_name varchar2(50) NOT NULL
);

CREATE TABLE vehicle_details (
  vehicle_id  number(10) primary key,
  company_id  number(10) references vehicle_mfg_company_details(company_id),
  vehicle_model_name varchar2(50) NOT NULL
);

CREATE OR REPLACE TYPE nestedTableEle
IS
OBJECT (
  vehicle_id NUMBER(10),
  vehicle_model_name VARCHAR2(50)
  );

-- nested table view column
CREATE OR REPLACE TYPE vehicle_details_list_ IS
  TABLE OF nestedTableEle;

CREATE OR REPLACE VIEW company_vehicles_view AS
  SELECT company.company_id,
         company.company_name,
         CAST (MULTISET (SELECT vehicle.vehicle_id, vehicle.vehicle_model_name
                         FROM vehicle_details vehicle
                         WHERE vehicle.company_id = company.company_id
                        )
                        AS vehicle_details_list_
              ) vehiclelist
FROM vehicle_mfg_company_details company;

-- no error.
INSERT INTO vehicle_mfg_company_details VALUES (101,'Ford');

-- error
INSERT INTO TABLE (
  SELECT vw.vehiclelist
  FROM company_vehicles_view vw
  WHERE company_id = 101
)
VALUES (1, 'EcoSport');

-- output
SQL Error: ORA-25015: cannot perform DML on this nested table view column
25015. 00000 -  "cannot perform DML on this nested table view column"
*Cause:    DML cannot be performed on a nested table view column except through
           an INSTEAD OF trigger
*Action:   Create an INSTEAD OF trigger over the nested table view column
           and then perform the DML.

CREATE OR REPLACE TRIGGER trg_comp_vehicles_view_insrt
  INSTEAD OF INSERT ON NESTED TABLE vehiclelist OF company_vehicles_view
  REFERENCING NEW AS Vehicle
              PARENT AS Company
  FOR EACH ROW
BEGIN
  -- Insert on nested table translates to insert on base table.
  INSERT INTO vehicle_details (
    vehicle_id,
    company_id,
    vehicle_model_name
  )
  VALUES (
    :Vehicle.vehicle_id,
    :Company.company_id,
    :Vehicle.vehicle_model_name
  );
END;

INSERT INTO TABLE (
  SELECT vw.vehiclelist
  FROM company_vehicles_view vw
  WHERE company_id = 101
)
VALUES (1, 'EcoSport');

INSERT INTO TABLE (
  SELECT vw.vehiclelist
  FROM company_vehicles_view vw
  WHERE company_id = 101
)
VALUES (2, 'Endeavour');

select * from vehicle_mfg_company_details;

select * from vehicle_details;