Introduction
Effective indexing is a crucial component of SQL Server performance tuning. Indexes are data structures that improve the speed of data retrieval operations on database tables. This document provides an overview of indexing strategies for SQL Server, including different index types, best practices, and considerations for index design.
Types of Indexes
SQL Server offers several types of indexes, each suited for different scenarios:
- Clustered Indexes: Determine the physical order of data in the table. Only one clustered index is allowed per table.
- Nonclustered Indexes: Point to rows in a table without defining the physical order. Can contain a copy of the key and a pointer to the base table.
- Columnstore Indexes: Designed for data warehousing and analytical workloads, providing high compression and fast scan performance.
- Filtered Indexes: Index a subset of rows based on a filter expression.
Best Practices for Index Design
Consider the following best practices when designing indexes:
- Analyze Query Patterns: Understand the queries that frequently access the table.
- Choose Appropriate Columns: Index columns frequently used in WHERE clauses, JOIN conditions, and ORDER BY clauses.
- Avoid Over-Indexing: Excessive indexes can degrade write performance and consume storage space.
- Regularly Maintain Indexes: Rebuild or reorganize indexes to maintain optimal performance.