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Learn T-SQL Querying

You're reading from   Learn T-SQL Querying A guide to developing efficient and elegant T-SQL code

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Product type Paperback
Published in Feb 2024
Publisher Packt
ISBN-13 9781837638994
Length 456 pages
Edition 2nd Edition
Languages
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Authors (2):
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Pedro Lopes Pedro Lopes
Author Profile Icon Pedro Lopes
Pedro Lopes
Pam Lahoud Pam Lahoud
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Pam Lahoud
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Table of Contents (18) Chapters Close

Preface 1. Part 1: Query Processing Fundamentals
2. Chapter 1: Understanding Query Processing FREE CHAPTER 3. Chapter 2: Mechanics of the Query Optimizer 4. Part 2: Dos and Don’ts of T-SQL
5. Chapter 3: Exploring Query Execution Plans 6. Chapter 4: Indexing for T-SQL Performance 7. Chapter 5: Writing Elegant T-SQL Queries 8. Chapter 6: Discovering T-SQL Anti- Patterns in Depth 9. Part 3: Assembling Our Query Troubleshooting Toolbox
10. Chapter 7: Building Diagnostic Queries Using DMVs and DMFs 11. Chapter 8: Building XEvent Profiler Traces 12. Chapter 9: Comparative Analysis of Query Plans 13. Chapter 10: Tracking Performance History with Query Store 14. Chapter 11: Troubleshooting Live Queries 15. Chapter 12: Managing Optimizer Changes 16. Index 17. Other Books You May Enjoy

Deconstructing table-valued functions

A User-Defined Function (UDF) is like a stored procedure in that it is a block of T-SQL statements saved as an object, but it differs in that it does not generate a result set; it returns a value of a specified type. A scalar UDF is a function that returns a single value; a Table-Valued Function (TVF) is a function that returns a table.

There are two types of TVFs in the SQL Database Engine:

  • Multi-statement TVFs (MSTVFs): MSTVFs declare a return table type, populate the table, then return the table at the end of the function
  • Inline TVFs: You can think of an inline TVF as a view that takes a parameter, the body of the function is a single query, and the return value is the result of that query

The following is an example of an MSTVF that we can create in the AdventureWorks sample database:

CREATE OR ALTER FUNCTION dbo.ufn_FindReports (@InEmpID INTEGER)
RETURNS @retFindReports TABLE
(
    EmployeeID int...
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