Please solve the following question.
You have a table `ORDERS` with columns `SHIPPING_DATE`, `DELIVERY_DATE`, and `RETURN_DATE`, all of which can be NULL. You want to find the first non-NULL date among these three columns for each order. Which SQL function is most appropriate and efficient for this task?
sqlCREATE TABLE ORDERS ( order_id NUMBER PRIMARY KEY, shipping_date DATE, delivery_date DATE, return_date DATE);INSERT INTO ORDERS VALUES (1, DATE '2023-01-01', DATE '2023-01-05', NULL);INSERT INTO ORDERS VALUES (2, NULL, DATE '2023-02-10', DATE '2023-02-15');INSERT INTO ORDERS VALUES (3, NULL, NULL, DATE '2023-03-20');INSERT INTO ORDERS VALUES (4, NULL, NULL, NULL);