PL/pgSQL Trigger

CREATE TABLE employees(
   id serial PRIMARY KEY,
   first_name VARCHAR(40) NOT NULL,
   last_name VARCHAR(40) NOT NULL
);

CREATE TABLE employee_audits (
   id serial PRIMARY KEY,
   employee_id int ,
   description VARCHAR(200),
   first_name VARCHAR(40) ,
   last_name VARCHAR(40) ,
   changed_on TIMESTAMP(6)
);

CREATE OR REPLACE FUNCTION log_last_name_changes()
  RETURNS TRIGGER AS
$BODY$
BEGIN
    IF NEW.last_name <> OLD.last_name THEN
        INSERT INTO employee_audits(employee_id, first_name, last_name, changed_on, description)
        VALUES(OLD.id, OLD.first_name, OLD.last_name, now(), CONCAT('Last Name Has Been Changed from ''', OLD.last_name, ''' to '' ', NEW.last_name));
    END IF;
    IF NEW.first_name <> OLD.first_name THEN
       INSERT INTO employee_audits(employee_id, first_name, last_name, changed_on, description)
       VALUES(OLD.id, OLD.first_name, OLD.last_name, now(), CONCAT('First Name Has Been Changed from ''', OLD.first_name, ''' to '' ', NEW.first_name));
   END IF;
    RETURN NEW;
END;
$BODY$
LANGUAGE plpgsql;

CREATE TRIGGER last_name_changes
  BEFORE UPDATE
  ON employees
  FOR EACH ROW
  EXECUTE PROCEDURE log_last_name_changes();

UPDATE employees
SET last_name = 'overandi'
WHERE ID = 2;

SELECT * FROM employees;
SELECT * FROM employee_audits;