CREATE TRIGGER reduceSalary BEFORE UPDATE OF salary ON person FOR EACH ROW WHEN (NEW.salary < OLD.salary) DECLARE lessMoney EXCEPTION; BEGIN RAISE lessMoney; EXCEPTION WHEN lessMoney THEN raise_application_error(-20001,'Attempt to reduce salary. Rejected!'); END;CREATE FUNCTION reduce_salary() RETURNS TRIGGER AS $reduceSalary$BEGIN IF NEW.salary < OLD.salary THEN RAISE EXCEPTION 'Salary cannot be reduced'; END IF; RETURN NEW;END;$reduceSalary$ LANGUAGE plpgsql;CREATE TRIGGER reduceSalaryBEFORE UPDATE ON personFOR EACH ROW EXECUTE PROCEDURE reduce_salary();