September 12, 2013 at 3:34 pm
Blimey? Must be some lingo local to Port Moresby.
Any way, since I don't think that there was a post with CROSS JOIN for unpivotting, here is an example, taken from another thread. When looking at the query plans, the CROSS APPLY solution looks better, but I would need more data to test. I would like to point out, though, that the solution with CROSS JOIN has the distinct advantage of being fully portable across platforms. (Hm, not all engines may support the VALUES clause, but it's easliy replaced with SELECT UNION ALL.)
Create Table #sample
( Name Varchar(100) PRIMARY KEY,
Mark1 int,
Mark2 int,
Mark3 int)
insert into #sample values ('Vignesh',100,59,95)
insert into #sample values ('ram',23,45,33)
insert into #sample values ('kumar',58,12,15)
insert into #sample values ('umar',15,25,98)
go
SELECT s.Name, CASE n.n WHEN 1 THEN s.Mark1
WHEN 2 THEN s.Mark2
WHEN 3 THEN s.Mark3
END AS Mark,
CASE n.n WHEN 1 THEN 'Mark1'
WHEN 2 THEN 'Mark2'
WHEN 3 THEN 'Mark3'
END AS MarkName
FROM #sample s
CROSS JOIN (VALUES (1), (2), (3)) AS n(n)
ORDER BY s.Name, n.n
go
SELECT s.Name, M.Mark, M.name
FROM #sample s
CROSS APPLY (VALUES (1, s.Mark1, 'Mark1'), (2, s.Mark2, 'Mark2'), (3, s.Mark1, 'Mark3')) AS M(n, Mark, name)
ORDER BY s.Name, M.n
go
DROP TABLE #sample
Note that here I have added a column n to the CROSS APPLY table to make that query fully equivalent to the CROSS JOIN solution, but in the APPLY solution you don't need n if you don't care about order, whereas it's a driving column in the CROSS JOIN solution.
As for UNPIVOT - I have never been able to learn it, the same with PIVOT.
[font="Times New Roman"]Erland Sommarskog, SQL Server MVP, www.sommarskog.se[/font]
September 12, 2013 at 9:19 pm
Erland Sommarskog (9/12/2013)
Blimey? Must be some lingo local to Port Moresby.
I didn't hear that much when I was out and about with my signboard.
I have it on good authority that Blimey is an exclusively British slang and that the Australian equivalent is Crikey, although the Tasmanian I heard that from is known for pulling my leg. There's a lot of Aussies in Port Moresby.
Now Pohmmie can refer to either Aussies (Prisoners Of Her Majesty) or Brits (turnabout is fair play) depending on who you talk to.
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?[/url]
Since random numbers are too important to be left to chance, let's generate some![/url]
Learn to understand recursive CTEs by example.[/url]
[url url=http://www.sqlservercentral.com/articles/St
September 13, 2013 at 1:01 am
Erland Sommarskog (9/12/2013)
Blimey? Must be some lingo local to Port Moresby.Any way, since I don't think that there was a post with CROSS JOIN for unpivotting, here is an example, taken from another thread. When looking at the query plans, the CROSS APPLY solution looks better, but I would need more data to test. I would like to point out, though, that the solution with CROSS JOIN has the distinct advantage of being fully portable across platforms. (Hm, not all engines may support the VALUES clause, but it's easliy replaced with SELECT UNION ALL.)
Create Table #sample( Name Varchar(100) PRIMARY KEY,
Mark1 int,
Mark2 int,
Mark3 int)
insert into #sample values ('Vignesh',100,59,95)
insert into #sample values ('ram',23,45,33)
insert into #sample values ('kumar',58,12,15)
insert into #sample values ('umar',15,25,98)
go
SELECT s.Name, CASE n.n WHEN 1 THEN s.Mark1
WHEN 2 THEN s.Mark2
WHEN 3 THEN s.Mark3
END AS Mark,
CASE n.n WHEN 1 THEN 'Mark1'
WHEN 2 THEN 'Mark2'
WHEN 3 THEN 'Mark3'
END AS MarkName
FROM #sample s
CROSS JOIN (VALUES (1), (2), (3)) AS n(n)
ORDER BY s.Name, n.n
go
SELECT s.Name, M.Mark, M.name
FROM #sample s
CROSS APPLY (VALUES (1, s.Mark1, 'Mark1'), (2, s.Mark2, 'Mark2'), (3, s.Mark1, 'Mark3')) AS M(n, Mark, name)
ORDER BY s.Name, M.n
go
DROP TABLE #sample
Note that here I have added a column n to the CROSS APPLY table to make that query fully equivalent to the CROSS JOIN solution, but in the APPLY solution you don't need n if you don't care about order, whereas it's a driving column in the CROSS JOIN solution.
As for UNPIVOT - I have never been able to learn it, the same with PIVOT.
Thanks for posting this - it's interesting to see both together. I'll have a closer look (in a couple of weeks, after vacation).
I've not been able to learn PIVOT and UNPIVOT either - a swift look at BOL is always necessary. Since they both look like quick-and-dirty implementations, I'll wait until MS rewrites them properly.
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
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