SQL Server Index

An index is a database object that improves the speed of data retrieval in a table at the expense of elsewhere and overhead in data transformation operations Indexes are important for optimal query performance by allowing SQL Server to search for rows that depending on the speed of indexed columns.

SQL Server indexing to optimize query performance

Indexes are often used effectively to improve query performance in SQL Server. Here is a structured approach to using SQL Server indexes for optimization,

Identify problematic Queries

Use query processing patterns- Analyze the processing patterns of your queries to see where most of the processing time is spent.
Profiler tool- SQL Server profiler or extensive information can help identify slow queries and execution times.

Understand indexing basics

Clustered- Physically groups data rows in a table based on indexed column(s).
Non-Clustered- Create a separate layout with indexed columns and a pointer to the actual row in the table.

Select Columns for indexing

Characters in WHERE clauses- Index characters used in WHERE clauses, especially those involving addition, subtraction, or comparison.
Columns in JOIN blocks- Index columns used to speed up join operations in the JOIN environment.
Characters in ORDER BY and GROUP BY- Index characters used in ORDER BY and GROUP BY clauses if these actions are operationally necessary.

Avoid Over-Indexing

Selective indexing- Create indexes on frequently used columns in queries but avoid creating indexes on rarely requested or updated columns.
Index Maintenance Overhead- Remember that indexes must be maintained during data conversion operations (insertions, updates, deletions).
 

Use Indexing Views and Indexed Computed Columns

Indexed Views- Pre-computed results that are physically stored as clustered indices or as non-clustered indices in the view.
Calculated numbers- Created index scores based on terms or functions.

Test and Monitor

Testing- Test query performance to ensure that indexes are used to check for improvement.
Monitoring- Constantly monitor database performance to identify new opportunities for improvement.

Example-

If you have any queries that frequently filter data based on the stuRollNO column in a large Students table, you can create a non-clustered index on stuRollNO  to speed up these queries,

USE MyCollegeDb
GO

CREATE NONCLUSTERED INDEX idstudents_sturollno 
ON Students(stuRollNO);

you can see the created above index in the SSMS just go to Object Explorer -> expand your database name (MyCollegeDb) -> expand the Tables folder then table name (Students) -> expand the Indexes folder and you can see the name of the created all indexed there like shown in below picture,

If you have a query that frequently extracts data based on the CustomerID column in a large Orders table, you can create a non-clustered index on the CustomerID to speed up these queries

By following these steps and principles, you can effectively use SQL Server indexing to optimize query performance and improve the overall responsiveness of your database application

Also, Read: Explain the SQL triggers and their uses