Database Reference
In-Depth Information
On to Chapter 7
This chapter describes fundamental information about the query optimizer. You've read about the inputs the query
optimizer uses to generate execution plans. You've also learned about the key components that compose the SQL
engine and how they interact with each other. And you've learned about query transformations and how they're
applied to increase the chances of finding the best possible execution plan for a given SQL statement.
System statistics is one of the inputs introduced in this chapter. Their purpose is to describe both the system
running the database engine and the runtime behavior of the storage subsystem. Chapter 7 describes in detail what
system statistics are, how to manage them, and how the query optimizer uses them to improve its estimations.
