Oracle PL/SQL – After DELETE Trigger example
This article shows you how to use AFTER DELETE TRIGGER
, it will fire after the delete operation is executed. In real life scenarios, it is mostly used for purposes like:
- Auditing or logging
1. After DELETE Trigger
In this example, if the user deleted a row of medical_bills
, the deleted row will be inserted into medical_bills_history
by after delete trigger on table medical_bills
1.1 Create tables and trigger.
medical_bills
CREATE TABLE medical_bills
(
BILL_ID number(10) primary key,
BILL_NUMBER varchar2(20),
PARTY_NAME varchar2(50),
BILL_DATE date,
CREATED_BY varchar2(20),
CREATED_DATE date
);
medical_bills_history
CREATE TABLE medical_bills_history
(
BILL_ID number(10),
BILL_NUMBER varchar2(20),
PARTY_NAME varchar2(50),
BILL_DATE date,
DELETED_BY varchar2(20),
DELETED_DATE date
);
trg_after_delete_bill
CREATE OR REPLACE TRIGGER trg_after_delete_bill
AFTER DELETE
ON medical_bills
FOR EACH ROW
DECLARE
username varchar2(10);
BEGIN
-- current login user, in this example, system
SELECT user INTO username FROM dual;
-- Insert OLD values in history table with username of user performing delete and sysdate as deleted_Date.
INSERT INTO medical_bills_history VALUES(:OLD.BILL_ID,
:OLD.BILL_NUMBER,:OLD.PARTY_NAME,:OLD.BILL_DATE,username,sysdate);
END;
1.2 Insert data for testing.
INSERT INTO MEDICAL_BILLS values (1,'BILL101','Peter Thomas','12-MAY-2016','HR',sysdate);
INSERT INTO MEDICAL_BILLS values (2,'BILL102','Jemes Petil','10-JUN-2016','HR',sysdate);
INSERT INTO MEDICAL_BILLS values (3,'BILL103','Fujit su','10-JUL-2015','HR',sysdate);
1.3 Display the data.
select * from MEDICAL_BILLS;
BILL_ID | BILL_NUMBER | PARTY_NAME | BILL_DATE | CREATED_BY | CREATED_DATE |
---|---|---|---|---|---|
1 | BILL101 | Peter Thomas | 12-MAY-2016 | HR | 18-JUN-2017 |
2 | BILL102 | Jemes Petil | 10-JUN-2016 | HR | 18-JUN-2017 |
3 | BILL103 | Fujit su | 10-JUL-2015 | HR | 18-JUN-2017 |
select * from MEDICAL_BILLS_HISTORY;
-- no result
1.4 Delete some rows from table MEDICAL_BILLS
DELETE FROM MEDICAL_BILLS WHERE bill_id = 1;
DELETE FROM MEDICAL_BILLS WHERE bill_id = 3;
1.5 Display the data again.
select * from MEDICAL_BILLS;
BILL_ID | BILL_NUMBER | PARTY_NAME | BILL_DATE | CREATED_BY | CREATED_DATE |
---|---|---|---|---|---|
2 | BILL102 | Jemes Petil | 10-JUN-2016 | HR | 18-JUN-2017 |
select * from MEDICAL_BILLS_HISTORY;
BILL_ID | BILL_NUMBER | PARTY_NAME | BILL_DATE | CREATED_BY | CREATED_DATE |
---|---|---|---|---|---|
1 | BILL101 | Peter Thomas | 12-MAY-2016 | SYSTEM | 18-JUN-2017 |
3 | BILL103 | Fujit su | 10-JUL-2015 | SYSTEM | 18-JUN-2017 |
‘Select user from dual..’ Means what.?
Why we are using that select statement
This statement ‘Select user from dual..’ will capture the user who deleted the records from Database Current Session.