What is an example of a type of Primary Index?

A Unique Primary Index is a specific type of index in Teradata that enforces the uniqueness of data in a table. When you define a Unique Primary Index for a table, you are ensuring that no two rows can have the same values for the columns that constitute that index. This is crucial for maintaining data integrity and can significantly enhance the efficiency of data retrieval. By allowing Teradata to quickly locate rows based on these unique keys, query performance is improved as well.

In the context of your question, this makes the Unique Primary Index the correct choice, as it directly pertains to the primary index functionality in Teradata. Other types of indexes like Non-Unique Secondary Index, Join Index, or having No Primary Index do not fulfill the criteria of being a primary index. For instance, Non-Unique Secondary Index allows for duplicate values and is used mainly for speeding up queries rather than enforcing uniqueness, while a Join Index is particularly useful for combining data from different tables efficiently. Finally, selecting No Primary Index indicates that the table lacks any indexing mechanism for data retrieval, which is not a prime characteristic of the primary index itself.