SQL index overview and strategy

SQL Server Index Structure and Concepts

Gathering SQL Server indexes statistics and usage information

Write Subqueries in Transact-SQL (Part 5 of 7) | Programming Databases with T-SQL for Beginners

Sort and Filter Results in Transact-SQL (Part 3 of 7) | Programming Databases with T-SQL for Beginners

Using SQL CREATE INDEX to create clustered and non-clustered indexes

Overview of SQL Server Clustered indexes

Designing effective SQL Server clustered indexes

SQL Server Query Execution Plans for beginners – NON-Clustered Index Operators