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

Query plan operators of interest

The different icons that are visible in a query execution plan are called operators. Logical operators describe a relational operation, such as, INNER JOIN. Physical operators implement the logical operation with a specific algorithm. So, when we examine a query plan, we are looking at physical operators.

Each physical operator represents a task that needs to be performed to complete the query, such as accessing data with a seek or a scan, joining data with a Hash Match or a Nested Loops, and sorting data. Some operators are especially relevant to understand while writing T-SQL that scales well. We will look at these operators, understand what they do, how they implement the physical operation behind the logical operation in T-SQL statements, and become familiar with aspects that will be important in the upcoming chapters where we explore T-SQL...