OCP CBT Question 590

Please solve the following question.

You are developing an application module that needs to guarantee that data read from the `ORDERS` table is not changed by other transactions before your transaction commits its own changes. Which SQL construct should you use?

Table Structure
CREATE TABLE ORDERS (
    order_id    NUMBER PRIMARY KEY,
    customer_id NUMBER,
    order_date  DATE,
    status      VARCHAR2(20)
);

SELECT order_id, status FROM ORDERS WHERE customer_id = 100 FOR UPDATE;

SET TRANSACTION ISOLATION LEVEL SERIALIZABLE; SELECT order_id, status FROM ORDERS WHERE customer_id = 100;

LOCK TABLE ORDERS IN EXCLUSIVE MODE; SELECT order_id, status FROM ORDERS WHERE customer_id = 100;

ALTER TABLE ORDERS LOCK; SELECT order_id, status FROM ORDERS WHERE customer_id = 100;