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SQL Server Query Tuning and Optimization

You're reading from  SQL Server Query Tuning and Optimization

Product type Book
Published in Aug 2022
Publisher Packt
ISBN-13 9781803242620
Pages 446 pages
Edition 1st Edition
Languages
Concepts
Author (1):
Benjamin Nevarez Benjamin Nevarez
Profile icon Benjamin Nevarez

Table of Contents (14) Chapters

Preface Chapter 1: An Introduction to Query Tuning and Optimization Chapter 2: Troubleshooting Queries Chapter 3: The Query Optimizer Chapter 4: The Execution Engine Chapter 5: Working with Indexes Chapter 6: Understanding Statistics Chapter 7: In-Memory OLTP Chapter 8: Understanding Plan Caching Chapter 9: The Query Store Chapter 10: Intelligent Query Processing Chapter 11: An Introduction to Data Warehouses Chapter 12: Understanding Query Hints Other Books You May Enjoy

Table variable deferred compilation

Similar to multistatement table-valued functions, table variables have the limitation that they do not support optimizer statistics and just provide one-row guess estimates. Table variable deferred compilation provides a solution to this problem. As its name suggests, this feature defers the optimization of a statement that references a table variable. By using table variable deferred compilation, the query processor can use the actual cardinality instead of the original guess of one.

Let’s translate our multistatement table-valued function example to a table variable using the following code. Since the scope of a table variable is a batch, you will need to run all three next statements, DECLARE, INSERT and SELECT, at the same time:

DECLARE @Sales TABLE (
 SalesOrderID int,
 SalesOrderDetailID int,
 CarrierTrackingNumber nvarchar(25),
 OrderQty smallint,
 ProductID int,
 SpecialOfferID int,
 UnitPrice money,
...
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