Stairway to Advanced T-SQL Level 6: Creating Rows Of Data Using The UNPIVOT Operator

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Stairway to Advanced T-SQL Level 6: Creating Rows Of Data Using The UNPIVOT Operator

Greg Larsen

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June 24, 2015 at 12:00 am

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Comments posted to this topic are about the item Stairway to Advanced T-SQL Level 6: Creating Rows Of Data Using The UNPIVOT Operator
Gregory A. Larsen, MVP
January 5, 2022 at 11:27 am

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g.britton SSChampion Points: 13863 More actions · Answer 1

Greg Larsen (4/27/2015)
Comments posted to this topic are about the item <A HREF="/articles/Stairway+Series/125504/">Stairway to Advanced T-SQL Level 6: Creating Rows Of Data Using The UNPIVOT Operator</A>

Consider using CROSS APPLY instead of UNPIVOT. More flexible (can unpivot multiple columns at once) and can generate better plans.

Unpivot a table using cross apply[/url]

Gerald Britton, Pluralsight courses

akljfhnlaflkj SSC Guru Points: 76202 More actions · Answer 2

I'm still a little confused, but good start for me anyway.

ChrisM@Work SSC Guru Points: 186127 More actions · Answer 3

g.britton (6/24/2015)
Greg Larsen (4/27/2015)
Comments posted to this topic are about the item <A HREF="/articles/Stairway+Series/125504/">Stairway to Advanced T-SQL Level 6: Creating Rows Of Data Using The UNPIVOT Operator</A>
Consider using CROSS APPLY instead of UNPIVOT. More flexible (can unpivot multiple columns at once) and can generate better plans.
Unpivot a table using cross apply[/url]

CROSS APPLY VALUES is a more specific term for the use of CROSS APPLY in a manual unpivot. Dwain's written a great article here[/url].

^{“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

g.britton SSChampion Points: 13863 More actions · Answer 4

ChrisM@Work (6/25/2015)
g.britton (6/24/2015)
Greg Larsen (4/27/2015)
Comments posted to this topic are about the item <A HREF="/articles/Stairway+Series/125504/">Stairway to Advanced T-SQL Level 6: Creating Rows Of Data Using The UNPIVOT Operator</A>
Consider using CROSS APPLY instead of UNPIVOT. More flexible (can unpivot multiple columns at once) and can generate better plans.
Unpivot a table using cross apply[/url]
CROSS APPLY VALUES is a more specific term for the use of CROSS APPLY in a manual unpivot. Dwain's written a great article here[/url].

Well it makes no difference if you use VALUES or SELECT with a UNION ALL. That is:

with cte as

(

select 1 as one, 2 as two, 3 as three, 4 as four

)

select a, b

from cte

cross apply

(

select one, two

union all

select three, four

--values (one,two),

-- (three,four)

) upvt(a, b)

works just the same if you comment the SELECTs in the cross apply and uncomment the VALUES. Granted, the second is a little less typing but the functionality is the same I believe (as is the actual execution plan, I think). I would even argue that the SELECT...UNION ALL is a little more flexible since you can add where clauses if needed

Gerald Britton, Pluralsight courses