Which index type provides an alternate path for data?

A secondary index provides an alternate path for data retrieval beyond the primary index. In Teradata, the primary index is crucial as it defines the distribution of data across the nodes of the system, allowing for efficient storage and access. However, when queries need to access data that is not aligned with the primary index, a secondary index comes into play.

Secondary indexes are especially useful when there are frequent queries on columns that are not the primary index. By creating a secondary index on these columns, Teradata allows the database to bypass the primary structure and access the required data more directly. This can significantly improve query performance for scenarios where the search patterns do not align with the primary index.

Other index types, like the join index or primary index, serve different roles. The join index is a specialized structure designed to optimize join operations between tables, while the primary index is foundational to how data is distributed and accessed. No index implies there is no indexing mechanism in place, negating any benefits of quick data retrieval. Therefore, the secondary index stands out as the correct choice for providing an alternate path for data.