There are four types of database triggers:
Table-level triggers can initiate activity before or after an INSERT, UPDATE, or DELETE event.
View-level triggers defines what can be done to the view.
Database-level triggers can be activated at startup and shutdown of a database.
Session-level triggers can be used to store specific information.
SQL>
SQL> create table company(
2 product_id number(4) not null,
3 company_id NUMBER(8) not null,
4 company_short_name varchar2(30) not null,
5 company_long_name varchar2(60)
6 );
Table created.
SQL> insert into company values(1,1001,'A Inc.','Long Name A Inc.');
1 row created.
SQL> insert into company values(1,1002,'B Inc.','Long Name B Inc.');
1 row created.
SQL> insert into company values(1,1003,'C Inc.','Long Name C Inc.');
1 row created.
SQL> insert into company values(2,1004,'D Inc.','Long Name D Inc.');
1 row created.
SQL> insert into company values(2,1005,'E Inc.','Long Name E Inc.');
1 row created.
SQL> insert into company values(2,1006,'F Inc.','Long Name F Inc.');
1 row created.
SQL>
SQL> create table product_audit(
2 product_id number(4) not null,
3 num_rows number(8) not null
4 );
Table created.
SQL>
SQL> CREATE OR REPLACE TRIGGER myTrigger
2 AFTER INSERT ON company
3 FOR EACH ROW
4 BEGIN
5 UPDATE product_audit
6 SET num_rows =num_rows+1
7 WHERE product_id =:NEW.product_id;
8 IF (SQL%NOTFOUND) THEN
9 INSERT INTO product_audit VALUES (:NEW.product_id,1);
10 END IF;
11 END;
12 /
Trigger created.
SQL>
SQL> drop table product_audit;
Table dropped.
SQL>
SQL> drop table company;
Table dropped.
SQL>