How to set new date entries to current date?

I am trying to create a trigger. It is supposed to update any new date ent开发者_如何转开发ry to sysdate. So far, I have the following code. However, I get "invalid table name" and "SQL statement ignored" errors.

CREATE OR REPLACE TRIGGER new_orders
AFTER INSERT ON orders
FOR EACH ROW
BEGIN
    IF INSERTING THEN
       UPDATE
           SET order_date := SYSDATE;
    END IF;
END;
/

---

CREATE OR REPLACE TRIGGER new_orders
BEFORE INSERT ON orders
FOR EACH ROW
BEGIN
    :NEW.order_date := SYSDATE;
END;
/