A . PRODUCT_ID can be assigned the PRIMARY KEY constraint.
In Oracle Database 12c, a PRIMARY KEY constraint is a combination of a NOT NULL constraint and a unique constraint. It ensures that the data contained in a column, or a group of columns, is unique among all the rows in the table and not null. Given the PRODUCT_ID is marked as NOT NULL, it is a candidate for being a primary key because we can assume that it is intended to uniquely identify each product in the table.
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B . EXPIRY_DATE cannot be used in arithmetic expressions. (Incorrect)
This statement is not necessarily true. Dates in Oracle can be used in arithmetic expressions, typically to add or subtract days from a date.
C . EXPIRY_DATE contains the SYSDATE by default if no date is assigned to it. (Incorrect) Unless explicitly specified, a date column does not default to SYSDATE. A default value must be set using the DEFAULT clause during the table creation or altered later.
D . PRODUCT_PRICE can be used in an arithmetic expression even if it has no value stored in it.
This is correct. In Oracle, if a numeric column like PRODUCT_PRICE has a NULL value (meaning no value stored in it), it can still be used in an arithmetic expression. In such expressions, NULL is typically treated as a zero, but the result of any arithmetic with NULL is also NULL.
E . PRODUCT_PRICE contains the value zero by default if no value is assigned to it. (Incorrect) Unless a default value is explicitly specified during the table creation or altered later, a numeric column like PRODUCT_PRICE does not automatically have a default value of zero.
F . PRODUCT_NAME cannot contain duplicate values. (Incorrect)
There is no constraint indicated that would prevent PRODUCT_NAME from containing duplicate values. Without a UNIQUE or PRIMARY KEY constraint, a column can contain duplicates.
The correct answers are A and D. PRODUCT_ID can be the primary key because it's specified as NOT NULL, thus it can uniquely identify each row in the table. PRODUCT_PRICE can be used in an arithmetic expression with the understanding that if it's NULL, the result of the expression would be NULL as well.