TRIGGER INSTEAD OF

Example 9-2 INSTEAD OF Trigger

This example creates the view oe.order_info to display information about customers and their orders. The view is not inherently updatable (because the primary key of the orders table, order_id, is not unique in the result set of the join view). The example creates an INSTEAD OF trigger to process INSERT statements directed to the view. The trigger inserts rows into the base tables of the view, customers and orders.

CREATE OR REPLACE VIEW order_info AS
   SELECT c.customer_id, c.cust_last_name, c.cust_first_name,
          o.order_id, o.order_date, o.order_status
   FROM customers c, orders o
   WHERE c.customer_id = o.customer_id;

CREATE OR REPLACE TRIGGER order_info_insert
   INSTEAD OF INSERT ON order_info
   DECLARE
     duplicate_info EXCEPTION;
     PRAGMA EXCEPTION_INIT (duplicate_info, -00001);
   BEGIN
     INSERT INTO customers
       (customer_id, cust_last_name, cust_first_name)
     VALUES (
     :new.customer_id,
     :new.cust_last_name,
     :new.cust_first_name);
   INSERT INTO orders (order_id, order_date, customer_id)
   VALUES (
     :new.order_id,
     :new.order_date,
     :new.customer_id);
   EXCEPTION
     WHEN duplicate_info THEN
       RAISE_APPLICATION_ERROR (
         num=> -20107,
         msg=> 'Duplicate customer or order ID');
   END order_info_insert;
/