In SQL Server indexing, which index type has a leaf (bottom) level that does not store the actual table data but instead stores pointers (row locators) to the data rows?

Introduction / Context:
Understanding how clustered and nonclustered indexes store information at the leaf level is essential for choosing the right indexing strategy for performance and storage.

Given Data / Assumptions:

• Leaf level behavior distinguishes index types.
• We are considering SQL Server's B-tree index structures.
• Terminology: leaf level = bottom level of the index.

Concept / Approach:

A clustered index's leaf level contains the data rows themselves (the table is ordered as the clustered index). A nonclustered index's leaf level contains key values plus row locators (RID or clustering key) that point to the underlying data.

Step-by-Step Solution:

Verification / Alternative check:

Query execution plans often show a Key Lookup/RID Lookup when a nonclustered index is used and additional columns are fetched from the base table via the locator.

Why Other Options Are Wrong:

Clustered: leaf contains data, not just pointers. Primary/Secondary: terminology not specific to SQL Server leaf-level storage.

Common Pitfalls:

Assuming “primary” means clustered; in SQL Server a primary key may be implemented as clustered or nonclustered.

Final Answer:

Nonclustered