When Do Indexed Views Outperform the Queries That Create Them?

Views vs. Queries: A Performance Comparison

A key question regarding database efficiency centers on the performance difference between using a view and executing the equivalent raw query. Specifically: Does a simple view query (SELECT * FROM myView) outperform its defining query (SELECT * FROM ([query creating myView's result set]))?

Understanding this requires examining the core distinctions between views and queries. Views are virtual tables, representing a data subset without physical storage. Queries, conversely, retrieve data dynamically.

Indexed Views: The Performance Game Changer

While basic views offer minimal performance gains, indexed views significantly improve efficiency. Microsoft's documentation emphasizes that indexed views:

• Materialize: Upon index creation, results are physically stored, eliminating runtime calculations.
• Query Optimization: The query optimizer may replace less efficient table references with the indexed view.

Microsoft's Documentation: Concrete Evidence

Microsoft SQL Server documentation explicitly states that creating a unique clustered index on a view materializes and persists its result set, thereby avoiding costly runtime processing. Furthermore, the documentation highlights that the query optimizer can utilize an indexed view directly or substitute it within a query plan for optimal performance.

Real-World Scenario: Indexed View's Advantage

Consider a global software company with millions of sales records. An indexed view containing only Lithuanian sales data would dramatically speed up data retrieval for this specific region. The index depth would reduce from 21 (Log2(1,000,000 )) without the indexed view to 7 (Log2(100)) with it—a threefold performance increase.

Indexed Views: More Than Just Glorified Indexes

The notion that indexed views are simply enhanced indexes on underlying tables is inaccurate. Microsoft documentation clarifies that indexed views provide performance benefits unattainable with standard indexes.

Conclusion: Indexed Views Reign Supreme

While simple views may not offer substantial performance improvements, indexed views offer considerable advantages. Their materialized results, persistent storage, and integration with query optimization typically result in superior performance compared to their defining queries. Therefore, indexed views prove invaluable for performance enhancement.

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