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An Alternative (Better?) Method to UNPIVOT (SQL Spackle)


An Alternative (Better?) Method to UNPIVOT (SQL Spackle)

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dwain.c
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Comments posted to this topic are about the item An Alternative (Better?) Method to UNPIVOT (SQL Spackle)


My mantra: No loops! No CURSORs! No RBAR! Hoo-uh!

My thought question: Have you ever been told that your query runs too fast?

My advice:
INDEXing a poor-performing query is like putting sugar on cat food. Yeah, it probably tastes better but are you sure you want to eat it?
The path of least resistance can be a slippery slope. Take care that fixing your fixes of fixes doesn't snowball and end up costing you more than fixing the root cause would have in the first place.


Need to UNPIVOT? Why not CROSS APPLY VALUES instead?
Since random numbers are too important to be left to chance, let's generate some!
Learn to understand recursive CTEs by example.
Splitting strings based on patterns can be fast!
My temporal SQL musings: Calendar Tables, an Easter SQL, Time Slots and Self-maintaining, Contiguous Effective Dates in Temporal Tables
Jeff Moden
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Very nicely done, Dwain.

You can also do similar with SELECT/UNION ALL in 2005.

--Jeff Moden

RBAR is pronounced ree-bar and is a Modenism for Row-By-Agonizing-Row.
First step towards the paradigm shift of writing Set Based code:
Stop thinking about what you want to do to a row... think, instead, of what you want to do to a column.
If you think its expensive to hire a professional to do the job, wait until you hire an amateur. -- Red Adair

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dwain.c
dwain.c
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Jeff Moden (8/2/2012)
Very nicely done, Dwain.

You can also do similar with SELECT/UNION ALL in 2005.


I love it when I attract attention from the big boys!

Thanks for the praise Blush and for stopping by.Hehe


My mantra: No loops! No CURSORs! No RBAR! Hoo-uh!

My thought question: Have you ever been told that your query runs too fast?

My advice:
INDEXing a poor-performing query is like putting sugar on cat food. Yeah, it probably tastes better but are you sure you want to eat it?
The path of least resistance can be a slippery slope. Take care that fixing your fixes of fixes doesn't snowball and end up costing you more than fixing the root cause would have in the first place.


Need to UNPIVOT? Why not CROSS APPLY VALUES instead?
Since random numbers are too important to be left to chance, let's generate some!
Learn to understand recursive CTEs by example.
Splitting strings based on patterns can be fast!
My temporal SQL musings: Calendar Tables, an Easter SQL, Time Slots and Self-maintaining, Contiguous Effective Dates in Temporal Tables
P Jones
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I was going to send the link to this to a colleague who's been learning unpivot BUT he'd probably be offended withthe mickey take at the top since his friend, another colleague, really is named Philip McCracken!
Basit Farooq
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Very nice article.

Regards,

Basit A. Farooq (MSC Computing, MCITP SQL Server 2005 & 2008, MCDBA SQL Server 2000)

http://basitaalishan.com
dennis.hafstrom
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Nice article.

I see Itzik using this approach a lot as well. Personally I like it but is stuck due to a third party program in an lower compatibility level quite often Crying
gsimard
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Thanks for the article, very interresting.

Basically, your "other Unpivot" technique is a brillant way to use the new (from 2008) Table Value Constructor

Using the same method, from your first example you could replace :

INSERT INTO #Orders
SELECT 1, NULL, 3 UNION ALL SELECT 2, 5, 4 UNION ALL SELECT 1, 3, 10



By the following :

INSERT INTO #Orders VALUES
(1, NULL, 3), (2, 5, 4), (1, 3, 10)



I don't think it's a real gain but maybe it's more readable.
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Very cool. Will have to dig into this and see whether or not it's something that is viable for use in my environment.


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Another cracking good article Dwain!

“Write the query the simplest way. If through testing it becomes clear that the performance is inadequate, consider alternative query forms.” - Gail Shaw

For fast, accurate and documented assistance in answering your questions, please read this article.
Understanding and using APPLY, (I) and (II) Paul White
Hidden RBAR: Triangular Joins / The "Numbers" or "Tally" Table: What it is and how it replaces a loop Jeff Moden
Exploring Recursive CTEs by Example Dwain Camps
WayneS
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Great article Dwain. I hadn't thought of trying the value constructor in the apply operator before... something new to play with.

Thanks!

Wayne
Microsoft Certified Master: SQL Server 2008
Author - SQL Server T-SQL Recipes
If you can't explain to another person how the code that you're copying from the internet works, then DON'T USE IT on a production system! After all, you will be the one supporting it!
Links: For better assistance in answering your questions, How to ask a question, Performance Problems, Common date/time routines,
CROSS-TABS and PIVOT tables Part 1 & Part 2, Using APPLY Part 1 & Part 2, Splitting Delimited Strings

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