In this chapter, you have learned how SQL Server stores and accesses data with and without indexes. Through analyzing query plans and I/O statistics, you have seen how important it is that the right indexes exist to optimize performance. You have learned when and how to use different index types (summarized in the table opposite) and how to maintain them.
You have seen that it is important to find the right index design and that the Database Engine Tuning Advisor can be a great help in building the index design.
Chapter 6 Quick Reference