Why can't I see inserted data in my view / tables - sql

Question

Firstly I created a table like this:
CREATE TABLE "DEPTT_DEMO1"
(
"DEPARTMENT_ID" NUMBER(4,0),
"DEPARTMENT_NAME" VARCHAR2(30 BYTE) CONSTRAINT "DEPT_NAME_NN1" NOT NULL ENABLE,
"MANAGER_ID" NUMBER(6,0),
"LOCATION_ID" NUMBER(4,0),
CONSTRAINT "DEPT_ID_PK1" PRIMARY KEY ("DEPARTMENT_ID")
);
After the table is created, I insert a few rows of data and then created a view like this:
CREATE OR REPLACE VIEW dept_demo_vw1
AS
SELECT DEPARTMENT_ID, DEPARTMENT_NAME, MANAGER_ID, LOCATION_ID
FROM DEPTT_DEMO1;
I create a trigger as well:
CREATE OR REPLACE TRIGGER vw_dept_tri
INSTEAD OF INSERT ON dept_demo_vw1
--declare
BEGIN
UPDATE dept_demo_vw1
SET DEPARTMENT_ID = dept_id.nextval
WHERE DEPARTMENT_ID IS NULL;
END vw_dept_tri;
After this when I try to insert data into the view, it says that the data is inserted, but I can't see any data in my view.

Answer 1

I don't know what you are doing, but you're doing it wrong.
INSTEAD OF trigger you wrote doesn't make much sense. It is instead of INSERT, but you are performing an UPDATE
Moreover, you are updating a view, but you should have been doing it on a table (not a view); that's why it is called "instead of" - instead of inserting into a view, you'd be inserting into a table
DEPTT_DEMO1.DEPARTMENT_ID is a primary key column. It means that it can not accept NULL values
Trigger's WHERE clause says WHERE DEPARTMENT_ID IS NULL; it is never NULL, that's a primary key column
Shortly, you'll have to think it over and do it properly.