1. T-Sql Dynamic Duo: Window Functions and C0mmon Table Expressions (CTE)

2. About me -Started my technical journey at this local SQL Saturday
-Microsoft Certified Professional
-Microsoft Technology Associate: Database Fundamentals
Day Job:
-Data Analyst with MoneySolvers in Jacksonville, FL
Blog at:
“How to Become Technical at Any Age” -
-Certified Lean Six Sigma Yellow Belt
-Weekend Sailor and Wanna-Be ‘Power BI Guru’
-Motto One: ‘Learn as much as you, as fast as you can for as long as you can.’
-Motto Two: ‘Be the best at what you do and learn more to be better!’

3. Session Overview Window Functions and CTEs Explained
Anatomy of a Window Function
Ranking Functions
Aggregate Functions and Percentages
Offset Functions
Framing Concepts and Running Totals
Median and More
Q & A as time allows
Information for this presentation taken primarily from Itzik Ben-Gan’s book: Microsoft SQL Server 2012 High Performance T-SQL Using Window Functions.

4. Meet the Real Dynamic Duo
Window Functions
Nothing to do with Windows operating system
Window Function performs a calculation over a set of rows
The Window is defined by the OVER clause
The OVER clause may contain a PARTITION BY option , Order BY option and/or Framing options.
CTE (Common Table Expressions)
Creates a temporary named result set that you can reference within a SELECT, INSERT, UPDATE, or DELETE statement
Begin a CTE with a WITH Clause and expression name: With CTE_C as (Select …..)
If more than one CTE, you must separate them with commas.
Great for troubleshooting code

5. Aggregate Functions
SUM()
COUNT()
MIN()
MAX()
AVG()
Offset Functions
Framing
LAG
LEAD
FIRST_VALUE
LAST_VALUE
NTH VALUE Not implemented with SQL Server 2012
Framing is another filter that further restricts the rows in a partition.

6. Anatomy of a Window Function
Function ( ) OVER Clause (Core Elements: Partitioning….Ordering…Framing)
Partition By option:
Restricts the rows into smaller sets.
Order By option: defines the ordering for the calculation
Framing option: Further restricts the rows in the partition and used in Aggregation and Offset functions

7. Demo Time

8. Window Function Recap Partitioning
-Suggest Filtering rather than Grouping
-Supported by ALL Window Functions
-If Partition By Clause not used, the window is NOT restricted [meaning
the ‘default’ partition is to consider the entire result set as one partition.
Ordering
-Defines the ordering for the Calculation, not presentational ordering
-Framing
- An additional option to further restrict the rows in the window partition
-Window Functions lend themselves to better optimization than subqueries.
-Not all Window Functions support all elements
-No major changes to Window Functions since release of SQL Server 2012, but 2016 has Batchmode Window Function performance improvements.

9. Resources
-’Microsoft SQL Server 2012 High_Performance T-SQL Using Window Functions’ by Itzik Ben-Gan [Great Book!]:
Search on Amazon
-Intro article to Window Functions:
-SQL Window Functions Introdution:
-CTE’s:
-OVER clause:
SQL 2019 Functionality:
Video by Itzik Ben-Gan
White Papers

10. Questions
Contact Info:
Blog:
LinkedIn: schneider /

11. THE END OF THE PRESENTATION
THE BEGINNING OF A LOVE FOR WINDOW FUNCTIONS AND CTES
Join me for the next session:
Women In Technology
I am on the panel 