SQL Server Interview Question #231

What is an index intersection?

Advanced Indexing Senior Advanced

Detailed Explanation

Index intersection occurs when SQL Server uses multiple indexes on the same table and combines their results to satisfy a query.

For example, one index may locate rows by CustomerId and another by StatusId, with the optimizer combining qualifying row locators.

This can be useful, but a well-designed composite or covering index may be more efficient for a critical repeated query. The actual execution plan and workload should determine whether redesign is justified.