Which three statements are true?

A. A customer can exist in many countries. This is true as customers can have multiple addresses or operations in different countries, and a database design can reflect this by allowing multiple country entries for a single customer1.

C. The statement will fail because subquery may not be I contained in a values clause. In Oracle Database 12c, a subquery cannot be used within the VALUES clause of an INSERT statement. The correct approach would be to use the subquery in conjunction with the INSERT INTO … SELECT syntax if multiple rows are derived from a subquery2.

F. A product can have a different unit price at different times. It is common for products to have different unit prices at different times due to various factors such as promotions, discounts, or changes in cost price. This can be represented in a database by having a price history table or a similar mechanism to track the changes in price over time1.

Note: The other options are incorrect because:

B. The statement about the SALES table failing if a row already exists for product 23 is not necessarily true. Oracle allows for multiple rows with the same product ID if the table is designed to handle such cases, like having a composite primary key or no constraints preventing duplicates.

D. Without specific information about the SALES table’s design, we cannot verify the number of foreign keys it has.

E. The statement about the successful execution and insertion of a new row into the SALES table is too vague without the context of the actual SQL statement being referred to.