Book Image

Learn T-SQL Querying

By : Pedro Lopes, Pam Lahoud
Book Image

Learn T-SQL Querying

By: Pedro Lopes, Pam Lahoud

Overview of this book

Transact-SQL (T-SQL) is Microsoft's proprietary extension to the SQL language used with Microsoft SQL Server and Azure SQL Database. This book will be a usefu to learning the art of writing efficient T-SQL code in modern SQL Server versions as well as the Azure SQL Database. The book will get you started with query processing fundamentals to help you write powerful, performant T-SQL queries. You will then focus on query execution plans and leverage them for troubleshooting. In later chapters, you will explain how to identify various T-SQL patterns and anti-patterns. This will help you analyze execution plans to gain insights into current performance, and determine whether or not a query is scalable. You will also build diagnostic queries using dynamic management views (DMVs) and dynamic management functions (DMFs) to address various challenges in T-SQL execution. Next, you will work with the built-in tools of SQL Server to shorten the time taken to address query performance and scalability issues. In the concluding chapters, this will guide you through implementing various features, such as Extended Events, Query Store, and Query Tuning Assistant, using hands-on examples. By the end of the book, you will have developed the skills to determine query performance bottlenecks, avoid pitfalls, and discover the anti-patterns in use.
Table of Contents (18 chapters)
Free Chapter
1
Section 1: Query Processing Fundamentals
5
Section 2: Dos and Donts of T-SQL
10
Section 3: Assemble Your Query Troubleshooting Toolbox

Understanding where QTA is needed

We discussed how the CE version is tied to the concept of database compatibility level in the Introducing the Cardinality Estimator section of Chapter 3, Mechanics of the Query Optimizer. The CE version that our databases use influences how query plans are calculated for queries that will execute in those databases. And we have seen first-hand the effects of the CE every time we compared the estimated number of rows with the actual number of rows throughout the book—for example in the Query plan comparison section of Chapter 10, Comparative Analysis of Query Plans, where we dealt with the row goal optimization.

When upgrading from older versions of SQL Server to Azure SQL Database and SQL Server 2016, or higher versions, we need to be conscious of how upgrading from CE 70 to a newer CE can affect our workloads—benefits are expected...