第 65 题 (多选题)： Examine the description of the PRODUCT_DETAILs table: Which two statements are true.

A. PRODUCT_NAME cannot contain duplicate values. B. EXPIRY_DATE contains the SYSDATE by default if no date is assigned to it . C. EXPIRY_DATE cannot be used in arithmetic expressions. D. PRODUCT_PRICE can be used in an arithmetic expression even if it has no value stored in it. E. PRODUCT_PRICE contains the value zero by default if no value is assigned to it. F. PRODUCT_ID can be assigned the PRIMARY KEY constraint 显示答案