Presentation about Trigger in Oracle database. Advanced Database Lab - Informatics Engineering, Bakrie University

1. Oracle Database
Trigger
Eryk Budi Pratama – Dimas Aryo Anggoro
Advanced Database Lab
Informatics Engineering –Bakrie University

2. Definition
• Trigger is a series of PL/SQL statements attached
to a database table that execute whenever a
triggering event (select, update, insert, delete)
occurs.
• Unlike stored procedures and functions, they
not explicitly called, but they are activated when
a triggering event occurs.
• Main purpose is to implement the complex
integrity constraints that can’t be done with the
CREATE TABLE or ALTER TABLE command.

3. Trigger Types
• Application Trigger
Trigger will be activated if there is an event on
certain application
• Database Trigger
Trigger will be activated if there is a data event
(DML Operation – Insert, Update, Delete) or
system event (logon or shutdown) on a schema
or database

4. Trigger Timing
• BEFORE
where a trigger will be activated before DML process on
table occur
• AFTER
where a trigger will be activated after DML process on
table occur
• INSTEAD OF
Trigger that just functionate on VIEW and usually used to
update data on complex view

5. Syntax
CREATE [OR REPLACE]
TRIGGER trigger_name
BEFORE (or AFTER)
INSERT OR UPDATE [OF COLUMNS] OR DELETE
ON tablename
[FOR EACH ROW [WHEN (condition)]]
BEGIN
...
END;

6. Example

7. Sample Table
CREATE TABLE PERSON (
ID INT,
NAME VARCHAR(30),
DOB DATE,
PRIMARY KEY(ID)
);

8. Before Insert Trigger
CREATE OR REPLACE
TRIGGER PERSON_INSERT_BEFORE
BEFORE
INSERT
ON PERSON
FOR EACH ROW
BEGIN
DBMS_OUTPUT.PUT_LINE(’BEFORE INSERT OF ’ ||
:NEW.NAME);
END;

9. (cont.)
• The single INSERT statement fires the trigger. When we
run it, we get the print out of ’BEFORE INSERT OF JOHN
DOE’.
SQL> INSERT INTO PERSON(ID,NAME,DOB) VALUES (1, ’ANI’
,SYSDATE);
BEFORE INSERT OF ANI
1 row created.

10. After Insert Trigger
CREATE OR REPLACE
TRIGGER PERSON_INSERT_AFTER
AFTER
INSERT
ON PERSON
FOR EACH ROW
BEGIN
DBMS_OUTPUT.PUT_LINE(’AFTER INSERT OF ’ || :NEW.NAME);
END;

11. (cont.)
SQL> INSERT INTO PERSON(ID,NAME,DOB) VALUES (2, ’BUDI’
,SYSDATE);
BEFORE INSERT OF BUDI
AFTER INSERT OF BUDI
1 row created.

12. Before Update Trigger
CREATE OR REPLACE
TRIGGER PERSON_UPDATE_S_BEFORE
BEFORE UPDATE
ON PERSON
BEGIN
DBMS_OUTPUT.PUT_LINE(’BEFORE UPDATING SOME
PERSON(S)’);
END;

13. (cont.)
SQL> UPDATE PERSON SET DOB = SYSDATE;
BEFORE UPDATING SOME PERSON(S)
2 rows updated

14. Managing Trigger
• Enable Trigger
ALTER TRIGGER trigger_name ENABLE
• Disable Trigger
ALTER TRIGGER trigger_name DISABLE
• Enable or Disable All Trigger
ALTER TABLE table_name DISABLE | ENABLE ALL TRIGGERS
• Delete TRIGGER
DROP TRIGGER nama_trigger

15. Permissions
Just like with procedures and functions, creating triggers
requires certain privileges which are not part of the default
privilege set.
GRANT CREATE TRIGGER TO <username>;

16. Q&A