【多项选择题】
Examine the SQL statement that creates ORDERS table:<br /> CREATE TABLE orders (SER_NO NUMBER UNIQUE, ORDER_ID NUMBER, ORDER_DATE DATE NOT NULL, STATUS VARCHAR2(10) CHECK (status IN ('CREDIT', 'CASH')), PROD_ID NUMBER REFERENCES PRODUCTS(PRODUCT_ID), ORD_TOTAL NUMBER, PRIMARY KEY (order_id, order_date));<br /> For which columns would an index be automatically created when you execute the above SQL statement? （）<p> Examine the SQL statement that creates ORDERS table:<br /> CREATE TABLE orders (SER_NO NUMBER UNIQUE, ORDER_ID NUMBER, ORDER_DATE DATE NOT NULL, STATUS VARCHAR2(10) CHECK (status IN ('CREDIT', 'CASH')), PROD_ID NUMBER REFERENCES PRODUCTS(PRODUCT_ID), ORD_TOTAL NUMBER, PRIMARY KEY (order_id, order_date));<br /> For which columns would an index be automatically created when you execute the above SQL statement? （）</p>
A、A. SER_NO
B、B. ORDER_ID
C、C. STATUS
D、D. PROD_ID
E、E. ORD_TOTAL
F、F. composite index on ORDER_ID and ORDER_DATE
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