Examine the SQL statements that creates ORDERS table: 
For which columns would an index be automatically created when you execute the above SQL statement? （）
- A、SER_NO
- B、ORDER_ID
- C、STATUS
- D、PROD_ID
- E、ORD_TOTAL
- F、Composite index on ORDER_ID and ORDER_DATE
正确答案:A,F
答案解析:有
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