Book Image

Learn T-SQL Querying - Second Edition

By : Pedro Lopes, Pam Lahoud
Book Image

Learn T-SQL Querying - Second Edition

By: Pedro Lopes, Pam Lahoud

Overview of this book

Data professionals seeking to excel in Transact-SQL (T-SQL) for Microsoft SQL Server and Azure SQL Database often lack comprehensive resources. This updated second edition of Learn T-SQL Querying focuses on indexing queries and crafting elegant T-SQL code, catering to all data professionals seeking mastery in modern SQL Server versions and Azure SQL Database. Starting with query processing fundamentals, this book lays a solid foundation for writing performant T-SQL queries. You’ll explore the mechanics of the Query Optimizer and Query Execution Plans, learning how to analyze execution plans for insights into current performance and scalability. Through dynamic management views (DMVs) and dynamic management functions (DMFs), you’ll build diagnostic queries. This book thoroughly covers indexing for T-SQL performance and provides insights into SQL Server’s built-in tools for expedited resolution of query performance and scalability issues. Further, hands-on examples will guide you through implementing features such as avoiding UDF pitfalls, understanding predicate SARGability, Query Store, and Query Tuning Assistant. By the end of this book, you‘ll have developed the ability to identify query performance bottlenecks, recognize anti-patterns, and skillfully avoid such pitfalls.
Table of Contents (18 chapters)
1
Part 1: Query Processing Fundamentals
4
Part 2: Dos and Don’ts of T-SQL
9
Part 3: Assembling Our Query Troubleshooting Toolbox

Accessing a query plan

To access estimated plans, which are a direct result of the optimization process, we can use either T-SQL commands or graphical tools. For the examples shown in this chapter, we use SQL Server Management Studio (SSMS).

Note

For most users, query plans in text format are harder to read and analyze; therefore, we will use graphical query plan examples throughout the book.

The SET command options SHOWPLAN_TEXT, SHOWPLAN_ALL, and SHOWPLAN_XML provide text-based information on query plans with different degrees of detail. Using any of these commands means the SQL Database Engine will not execute the T-SQL statements but show the query plan as produced by the Query Optimizer.

Take an example of a query that can be executed in the scope of the AdventureWorks sample database:

SELECT pp.FirstName, pp.LastName, pa.AddressLine1, pa.City, pa.PostalCode
FROM Person.Address AS pa
INNER JOIN Person.BusinessEntityAddress AS pbea ON pa.AddressID = pbea.AddressID...