Cải thiện hiệu năng truy vấn trong SQL Server

In this chapter, students will learn how SQL code formatting, commenting, and aliasing is used to make queries easy to read and understand. Students will also be introduced to query processing order in the database versus the order of the SQL syntax in a query.

This chapter introduces filtering with WHERE and HAVING and some best practices for how (and how not) to use these keywords. Next, it explains the methods used to interrogate data and the effects these may have on performance. Finally, the chapter goes over the roles of DISTINCT() and UNION in removing duplicates and their potential effects on performance.

This chapter is an introduction to sub-queries and their potential impacts on query performance. It also examines the different methods used to determine if the data in one table is present, or absent, in a related table.

Students are introduced to how STATISTICS TIME, STATISTICS IO, indexes, and executions plans can be used in SQL Server to help analyze and tune query performance.