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Learn T-SQL Querying

You're reading from   Learn T-SQL Querying A guide to developing efficient and elegant T-SQL code

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Product type Paperback
Published in May 2019
Publisher Packt
ISBN-13 9781789348811
Length 484 pages
Edition 1st Edition
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Authors (2):
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Pedro Lopes Pedro Lopes
Author Profile Icon Pedro Lopes
Pedro Lopes
Pam Lahoud Pam Lahoud
Author Profile Icon Pam Lahoud
Pam Lahoud
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Table of Contents (18) Chapters Close

Preface 1. Section 1: Query Processing Fundamentals FREE CHAPTER
2. Anatomy of a Query 3. Understanding Query Processing 4. Mechanics of the Query Optimizer 5. Section 2: Dos and Donts of T-SQL
6. Exploring Query Execution Plans 7. Writing Elegant T-SQL Queries 8. Easily-Identified T-SQL Anti-Patterns 9. Discovering T-SQL Anti-Patterns in Depth 10. Section 3: Assemble Your Query Troubleshooting Toolbox
11. Building Diagnostic Queries Using DMVs and DMFs 12. Building XEvent Profiler Traces 13. Comparative Analysis of Query Plans 14. Tracking Performance History with Query Store 15. Troubleshooting Live Queries 16. Managing Optimizer Changes with the Query Tuning Assistant 17. Other Books You May Enjoy

Query optimization essentials

The Query Processor is also the component inside the SQL Server Database Engine that is responsible for query optimization. This is the second stage of query processing and its goal is to produce a query plan that can then be cached for all subsequent uses of the same query. In this section, we will focus on the highlighted sections of the following diagram, which handle query optimization:

SQL Server uses cost-based optimization, which means that the Query Optimizer is driven mostly by estimations of the required cost to access and transform data (such as joins and aggregations) that will produce the intended result set. The purpose of the optimization process is to reasonably minimize the I/O, memory, and compute resources needed to execute a query in the fastest way possible. But it is also a time-bound process and can time out. This means that...

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