Comparing figures based on relative date

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Comparing figures based on relative date

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Paul Munter Say Hey Kid Points: 681 More actions · Answer 1

Agree in this scenario it's for a BI application and I doubt it can handle self joins, throw in the fact it's been dimensionally modelled and it adds it a fair bit more complexity. I literally took it back to bare bones in order to try and break it down a bit then build it back up.

I'm too spoiled now with ETL tools and not close enough to the real action anymore 😀

Again thanks for the responses much appreciated.

ScottPletcher SSC Guru Points: 101126 More actions · Answer 2

For best performance,

Cluster the table by

LAST_DAY_OF_MONTH

and not the dopey identity column. If you still need the identity (??), you can leave it as the nonclustered pk.

SQL DBA,SQL Server MVP(07, 08, 09) "It's a dog-eat-dog world, and I'm wearing Milk-Bone underwear." "Norm", on "Cheers". Also from "Cheers", from "Carla": "You need to know 3 things about Tortelli men: Tortelli men draw women like flies; Tortelli men treat women like flies; Tortelli men's brains are in their flies".

Dwain Camps SSC Guru Points: 86978 More actions · Answer 3

ChrisM@Work (2/11/2013)
Something like this?
DROP TABLE #mytable
CREATE TABLE #mytable
(P_KEY INT IDENTITY(1,1) PRIMARY KEY CLUSTERED,
LAST_DAY_OF_MONTH DATETIME,
Value int,
PreviousYearValue INT)
INSERT INTO #mytable
VALUES('20130131',20,NULL),('20120131',5,NULL),('20130331',40,NULL),('20120331',2,NULL)
SELECT
ty.*,
ly.*
FROM #mytable ty
LEFT JOIN #mytable ly
ON ly.LAST_DAY_OF_MONTH = DATEADD(yy,-1,ty.LAST_DAY_OF_MONTH)

This may be an alternative:

CREATE TABLE #mytable

(P_KEY INT IDENTITY(1,1) PRIMARY KEY CLUSTERED,

LAST_DAY_OF_MONTH DATETIME,

Value int,

PreviousYearValue INT)

INSERT INTO #mytable

VALUES('20130131',20,NULL),('20120131',5,NULL),('20130331',40,NULL),('20120331',2,NULL)

SELECT P_Key=MIN(P_Key), LAST_DAY_OF_MONTH, Value=SUM(Value), PreviousYearValue=SUM(PreviousYearValue)

FROM (

SELECT P_Key, LAST_DAY_OF_MONTH, Value, PreviousYearValue

FROM #mytable

UNION ALL

SELECT P_Key, DATEADD(year, 1, LAST_DAY_OF_MONTH), NULL, Value

FROM #mytable) a

GROUP BY LAST_DAY_OF_MONTH

HAVING SUM(Value) IS NOT NULL

DROP TABLE #mytable

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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]
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ChrisM@Work SSC Guru Points: 186127 More actions · Answer 4

ScottPletcher (2/11/2013)
For best performance,
Cluster the table by
LAST_DAY_OF_MONTH
and not the dopey identity column. If you still need the identity (??), you can leave it as the nonclustered pk.

+1

^{“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

MMartin1 One Orange Chip Points: 27799 More actions · Answer 5

Agree in this scenario it's for a BI application and I doubt it can handle self joins

Maybe I am reading you wrong but I take it you are writing the logic in the application and performance is your concern? Have the application call a sql server stored procedure where the user can supply the date range for the normal dates (not the ones one year ago).

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