1. T-SQL Power! The OVER Clause: Your Key to No-Sweat Problem Solving
Tech Ed North America 2010
11/18/2018 2:11 PM
Required Slide
SESSION CODE: DAT317
T-SQL Power! The OVER Clause: Your Key to No-Sweat Problem Solving
Adam Machanic
Database Consultant
SQLblog
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

2. WHAT IS POWER?

4. INNOVATION
SHOULD
BE EASY!

5. About Me amachanic@gmail.com
Independent SQL Server and .NET Consultant
Boston, MA
Author SQL Server 2008 Internals
Expert SQL Server 2005 Development
Conference and INETA Speaker
Connections, PASS, TechEd, DevTeach, etc.
Co-Founder: SQLblog.com
The SQL Server Blog Spot on the Web

6. Grouping vs. Partitioning
Grouping is an N1 transformation {
ColA
ColB
Val A B 1 2 3 C D 4 5
3 rows  1 row {
2 rows  1 row

7. Grouping vs. Partitioning
Grouping is an N1 transformation
ColA
ColB
SUM(Val) A B 6 C D 9 {
1 row {
1 row
We gain insight, but lose information

8. Grouping vs. Partitioning
Partitioning is an NN transformation {
ColA
ColB
Val A B 1 2 3 C D 4 5
3 rows  3 rows {
2 rows  2 rows

9. Grouping vs. Partitioning
Partitioning is an NN transformation {
ColA
ColB
Val
SUM(Val) OVER (…) A B 1 6 2 3 C D 4 9 5
3 rows {
2 rows
We gain insight, and lose nothing

10. Introducing the OVER Clause
First available in SQL Server 2005
Can be applied to any system or user-defined aggregate for partitioning
Can be applied to a new set of “windowed” functions for ordered metrics

11. Aggregation: The Old Way
Tech Ed North America 2010
11/18/2018 2:11 PM
Aggregation: The Old Way
SELECT
ColA,
ColB,
SUM(Val)
FROM T1
GROUP BY
ColB
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

12. Aggregation: With OVER
SELECT
ColA,
ColB,
SUM(Val) OVER (
PARTITION BY
ColB )
FROM T1

13. We Aren’t Required to Partition…
SELECT
ColA,
ColB,
SUM(Val) OVER()
FROM T1

14. Multiple Partitions in One Query? Sure.
SELECT
ColA,
ColB,
SUM(Val) OVER (
PARTITION BY
ColB
) AS PartitionedVal,
SUM(Val) OVER() AS NonPartitionedVal
FROM T1

15. Ranking and Numbering Functions
SQL Server 2005/2008 windowing functions:
ROW_NUMBER
RANK
DENSE_RANK
NTILE
These functions can be both partitioned and ordered

16. ROW_NUMBER Uniquely numbers rows
Tech Ed North America 2010
11/18/2018 2:11 PM
ROW_NUMBER Uniquely numbers rows
ColA
ColB
ROW_NUMBER() OVER
(ORDER BY ColA) A Z 1 B Y 2 C X 3 D W 4 E V 5
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

17. Tech Ed North America 2010
11/18/2018 2:11 PM
ROW_NUMBER – Partitioned Uniquely numbers rows, restarting at each partition
ColA
ColB
ROW_NUMBER() OVER
(PARTITION BY ColA ORDER BY ColB) A X 1 Y 2 Z 3 B
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

18. RANK Ranks rows, skipping numbers for ties
Tech Ed North America 2010
11/18/2018 2:11 PM
RANK Ranks rows, skipping numbers for ties
ColA
ColB
RANK() OVER
(ORDER BY ColA) A Z 1 Y B X 3 W C V 5
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

19. DENSE_RANK Ranks rows, not skipping numbers for ties
Tech Ed North America 2010
11/18/2018 2:11 PM
DENSE_RANK Ranks rows, not skipping numbers for ties
ColA
ColB
DENSE_RANK() OVER
(ORDER BY ColA) A Z 1 Y B X 2 W C V 3
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

20. NTILE(x) Creates closest-match subgroups based on desired size “x”
Tech Ed North America 2010
11/18/2018 2:11 PM
NTILE(x) Creates closest-match subgroups based on desired size “x”
ColA
ColB
NTILE(3) OVER
(ORDER BY ColA) A Z 1 Y B X W 2 C V
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

21. Under the Covers You didn’t think this was all free—right?
Partitioning and ordering both require input rows to be sorted
Indexes can be aligned to reduce or eliminate the need to sort
All of the partitioning work is done with the Segment iterator
Watch out for spools!

22. And Now:
A Bunch of Demos!

23. The OVER Clause, In Depth!
demo

24. Summary The OVER clause makes powerful T-SQL easy…
…and perhaps even fun
Great performance if you do a bit of work upfront
Don’t forget to be creative!

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© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

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© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

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© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

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29. Tech Ed North America 2010 11/18/2018 2:11 PM
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.

30. Required Slide Tech Ed North America 2010 11/18/2018 2:11 PM
© 2010 Microsoft Corporation. All rights reserved. Microsoft, Windows, Windows Vista and other product names are or may be registered trademarks and/or trademarks in the U.S. and/or other countries.
The information herein is for informational purposes only and represents the current view of Microsoft Corporation as of the date of this presentation. Because Microsoft must respond to changing market conditions, it should not be interpreted to be a commitment on the part of Microsoft, and Microsoft cannot guarantee the accuracy of any information provided after the date of this presentation. MICROSOFT MAKES NO WARRANTIES, EXPRESS, IMPLIED OR STATUTORY, AS TO THE INFORMATION IN THIS PRESENTATION.