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

EXECUTE versus sp_executesql

There are times when an application must build a T-SQL statement dynamically before executing it on the server. In order to execute a dynamically created T-SQL statement, we can use either the EXECUTE command or the sp_executesql stored procedure. The sp_executesql procedure is the preferred method for executing dynamic T-SQL because it allows us to add parameter markers and thus increases the likelihood that the SQL Database Engine will be able to reuse the plan and avoid costly query compilations.

Here’s an example script from the AdventureWorks database that builds a dynamic T-SQL statement and executes it via the EXECUTE command:

DECLARE @sql nvarchar(MAX), @JobTitle nvarchar(50) = N'Sales Representative';
SET @sql = 'SELECT e.BusinessEntityID, p.FirstName, p.LastName
FROM HumanResources.Employee e
INNER JOIN Person.Person p ON p.BusinessEntityID = e.BusinessEntityID
WHERE e.JobTitle = N''' + @JobTitle + &apos...