Triggers A trigger is a stored subprogram associated with a table, view, or event. The trigger can be invoked once, when some event occurs, or many times, once for each row affected by an INSERT, UPDATE, or DELETE statement. The trigger can be invoked before or after the event. The trigger in example is invoked whenever salaries in the employees table are updated. For each update, the trigger writes a record to the emp_audit table. Example: Creating a Trigger SQL> CREATE TABLE emp_audit ( 2 emp_audit_id NUMBER(6), 3 up_date DATE, 4 new_sal NUMBER(8,2), 5 old_sal NUMBER(8,2) 6 ); Table created. SQL> CREATE OR REPLACE TRIGGER audit_sal 2 AFTER UPDATE OF salary 3 ON employees 4 FOR EACH ROW 5 BEGIN 6 INSERT INTO emp_audit 7 VALUES(:old.employee_id,SYSDATE,:new.salary, :old.salary); 8 END; 9 / Trigger created. SQL> update employees set salary=5000 2 where salary < 3000;
TriggersA trigger is a stored subprogram associated with a
table, view, or event. The trigger can be invoked once, when some
event occurs, or many times, once for each row affected by an
INSERT, UPDATE, or DELETE statement. The trigger can be invoked
before or after the event.The trigger in example is invoked
whenever salaries in the employees table are updated. For each
update, the trigger writes a record to the emp_audit
table.Example:Creating a TriggerSQL> CREATE TABLE emp_audit (2
emp_audit_id NUMBER(6),3 up_date DATE,4 new_sal NUMBER(8,2),5
old_sal NUMBER(8,2)6 );Table created.SQL> CREATE OR REPLACE
TRIGGER audit_sal2 AFTER UPDATE OF salary3 ON employees4 FOR EACH
ROW5 BEGIN6 INSERT INTO emp_audit7
VALUES(:old.employee_id,SYSDATE,:new.salary, :old.salary);8 END;9
/Trigger created.SQL> update employees set salary=50002 where
salary < 3000;24 rows updated.
