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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
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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

Fixing regressed queries

Parameters are fundamental drivers of the query optimization process. We discussed the topic of parameter sensitivity, known as parameter sniffing, in the The importance of parameters section of Chapter 2, Understanding Query Processing, and the Query plan properties of interest section in Chapter 4, Exploring Query Execution Plans.

This brings us to the other main benefit of the Query Store: tracking plan changes over time—in other words, regressions from parameter-sensitive plans. With this exercise, we want to make sure that the volatility that can come with parameter-sensitive plans is addressed, and that the plan that is used is the one that's best for most uses, if not all. If successful, we will address the complaints we've been getting that sometimes the application just slows down for a few minutes, and then recovers.

To generate...

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