Book Image

SQL Server Query Tuning and Optimization

By : Benjamin Nevarez
Book Image

SQL Server Query Tuning and Optimization

By: Benjamin Nevarez

Overview of this book

SQL Server is a relational database management system developed by Microsoft. As a database server, it is a software product with the primary function of storing and retrieving data as requested by other software applications. This book starts by describing the inner workings of the query optimizer, and will enable you to use this knowledge to write better queries and provide the query engine with all the information it needs to produce efficient execution plans. As you progress, you’ll get practical query optimization tips for troubleshooting underperforming queries. The book will also guide you through intelligent query processing and what is new in SQL Server 2022. Query performance topics such as the Query Store, In-Memory OLTP and columnstore indexes are covered as well. By the end of this book, you’ll be able to get the best possible performance for your queries and applications.
Table of Contents (14 chapters)

Understanding index operations

In a seek operation, SQL Server navigates throughout the B-tree index to quickly find the required records without the need for an index or table scan. This is similar to using an index at the end of a book to find a topic quickly, instead of reading the entire book. Once the first record has been found, SQL Server can then scan the index leaf level forward or backward to find additional records. Both equality and inequality operators can be used in a predicate, including =, <, >, <=, >=, <>, !=, !<, !>, BETWEEN, and IN. For example, the following predicates can be matched to an Index Seek operation if there is an index on the specified column or a multicolumn index with that column as a leading index key:

  • ProductID = 771
  • UnitPrice < 3.975
  • LastName = ‘Allen’
  • LastName LIKE ‘Brown%’

As an example, look at the following query, which uses an Index Seek operator and produces...