# Functionality Summary: Scan vs Seek per Storage Structure > [!Note] > SQL Server selects either a [[Scan Operator]] or [[Seek Operator]] depending on the underlying storage structure and the selectivity of the query predicate. | **Storage Structure** | **Scan Operator** | **Seek Operator** | | ----------------------- | --------------------------------- | --------------------------------- | | [[Heap]] | [[Table Scan Operator]] | — | | [[Clustered Index]] | Clustered [[Index Scan Operator]] | Clustered [[Index Seek Operator]] | | [[Non-Clustered Index]] | [[Index Scan Operator]] | [[Index Seek Operator]] | --- ## References - Korotkevitch, D. (2022). _SQL Server advanced troubleshooting and performance tuning: Best practices and techniques_. O’Reilly Media. - Nevarez, B. (2022). _SQL Server query tuning and optimization: Optimize Microsoft SQL Server 2022 queries and applications_. Packt Publishing.