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: 101103 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: 86948 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.

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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: 27795 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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