PLSQL :NEW and :OLD

Question

Can anyone help me understand when to use :NEW and :OLD in PLSQL blocks, I\'m finding it very difficult to understand their usage.

Answer 1

A simple example that shows the use of old and new using triggers

CREATE TABLE emp_log(
emp_id NUMBER;
updated_by DATE,
new_salary VARCHAR2(15),
Action VARCHAR2(20));

CREATE OR REPLACE TRIGGER log_sal 
AFTER UPDATE OF sal on emp
FOR EACH ROW
BEGIN
INSERT INTO emp_log( emp_id, updated_by, new_salary, Action)
VALUES(:NEW.empno, USER, :NEW.sal, 'New salary');
END;
/