Oracle trigger- instead of delete, update the row - sql

Question

How do I write an Oracle trigger, than when a user deletes a certain record, the delete doesnt actually happen, but instead performs an update on those rows and sets the status of the record to 'D'?
I tried:
create or replace
trigger DELFOUR.T4M_ITEM_ONDELETE
before delete on M_ITEM_H
FOR EACH ROW
BEGIN
UPDATE
M_ITEM_H
SET
ITEM_STAT = 'D'
WHERE
CUST_CODE = 'TEST'
AND ITEM_CODE = 'GDAY'
;
raise_application_error(-20000,'Cannot delete item');
END;
But I am getting mutating table errors. Is this possible?

Answer 1

If you really need a trigger, the more logical approach would be to create a view, create an INSEAD OF DELETE trigger on the view, and to force the applications to issue their deletes against the view rather than against the base table.
CREATE VIEW vw_m_item_h
AS
SELECT *
FROM m_item_h;
CREATE OR REPLACE TRIGGER t4m_item_ondelete
INSTEAD OF DELETE ON vw_m_item_h
FOR EACH ROW
AS
BEGIN
UPDATE m_item_h
SET item_stat = 'D'
WHERE <<primary key>> = :old.<<primary key>>;
END;
Better yet, you would dispense with the trigger, create a delete_item procedure that your application would call rather than issuing a DELETE and that procedure would simply update the row to set the item_stat column rather than deleting the row.
If you really, really, really want a solution that involves a trigger on the table itself, you could
Create a package with a member that is a collection of records that map to the data in the m_item_h table
Create a before delete statement-level trigger that empties this collection
Create a before delete row-level trigger that inserts the :old.<<primary key>> and all the other :old values into the collection
Create an after delete statement-level trigger that iterates through the collection, re-inserts the rows into the table, and sets the item_stat column.
This would involve more work than an instead of trigger since you'd have to delete and then re-insert the row and it would involve way more moving pieces so it would be much less elegant. But it would work.

Answer 2

First of all the trigger you wrote would throw a mutating table error. Technically what you are asking is not possible i.e. delete wouldn't delete but rather update, unless you raise an exception in the middle which could be an ugly way of doing it. I would think users using some sort of application front end which lets them delete data using a delete button, so you may use an update statement there instead of a delete statement.
Another option would be to create a log table, where you could insert the record before deleting it from the actual table and then join the log table with the actual table to retrieve deleted records. Something like-
CRETAE TABLE M_ITEM_H_DEL_LOG as SELECT * FROM M_ITEM_H WHERE 1=2;
And then
create or replace
trigger DELFOUR.T4M_ITEM_ONDELETE
before delete on M_ITEM_H
FOR EACH ROW
BEGIN
INSERT INTO
M_ITEM_H_DEL_LOG
VALUES (:old.col1, :old.col2,.....) --col1, col2...are columns in M_ITEM_H
;
END;