To answer this question, you need to understand the concept of privileges in a database. Privileges control what actions can be performed on database objects, such as selecting data from a table or modifying its structure.
Let's go through each option to understand why it is correct or incorrect:
Option A) Index - The SELECT privilege cannot be controlled on an index. An index is a database object that improves the performance of queries by allowing faster data retrieval. However, it does not store the actual data itself, so there is no need to control the SELECT privilege on an index.
Option B) Sequence - The SELECT privilege cannot be controlled on a sequence. A sequence is a database object that generates unique numbers, typically used for generating primary key values. The SELECT privilege is not relevant for sequences as they are not queried like tables or views.
Option C) Nickname - The SELECT privilege can be controlled on a nickname. A nickname is a database object that provides a local name or alias for a remote table or view in a distributed database system. Controlling the SELECT privilege on a nickname allows you to determine who can access the remote data through the nickname.
Option D) View - The SELECT privilege can be controlled on a view. A view is a virtual table based on the result of a query. By controlling the SELECT privilege on a view, you can restrict who can retrieve data from the view, providing an additional layer of security.
The correct answer is C) Nickname and D) View. These options are correct because the SELECT privilege can be controlled on both nicknames and views to regulate access to the data they represent.