Compare this years data with last years data - day adjusted

Question

Compare this years data with last years data - day adjusted

ps_vbdev

SSCarpal Tunnel

Points: 4060
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May 25, 2015 at 10:06 am

#304279

Hi all
our business get orders through the week with the weekends (Fri & Sat) orders being higher than weekdays. Im wanting to graph this years data with last years and possible the years before but to compare days in such a way that the all the weekdays line up. so comparing 2015 week 1 with 2014 week 1 but with 03/01/2015 (Sat) lining up with 04/01/2014 (Sat) etc.
I'm looking for alternatives to adding or removing days from the dates to solve this issue, i have a date dimension table for the past 5 years that i can use to compare calendar week 201401 with calendar week 201501 but im finding it a bit inflexable. Has anyone else ever had this problem.
Many thanks.

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pietlinden SSC Guru Points: 63503 More actions · Answer 1

Shouldn't you be able to join on WeekOfYear and DayOfWeek? Then you should be golden, right?

Sounds like you might be missing some columns in your Calendar table. Can you post the create table script of the Calendar table?

Jeff Moden SSC Guru Points: 1004356 More actions · Answer 2

Use ISOWEEK for this.

--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.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)

Y.B. SSChampion Points: 11649 More actions · Answer 3

It's much easier to visualize with data.

Try this for example:

DECLARE @test-2 TABLE(myDate DATE, Sales MONEY)

INSERT INTO @test-2(myDate, Sales)

VALUES

('12/30/2013',100),

('12/31/2013',100),

('01/01/2014',100),

('01/02/2014',100),

('01/03/2014',200),

('01/04/2014',200),

('01/05/2014',100),

('01/06/2014',100),

('01/07/2014',100),

('01/08/2014',100),

('01/09/2014',100),

('01/10/2014',250),

('01/11/2014',250),

('01/01/2015',100),

('01/02/2015',150),

('01/03/2015',150),

('01/04/2015',100),

('01/05/2015',100),

('01/06/2015',100),

('01/07/2015',100),

('01/08/2015',100),

('01/09/2015',300),

('01/10/2015',300)

SELECT *, DATEPART(dw, myDate) AS Day_Week, DATEPART(isowk, myDate) AS Week_Num FROM @test-2

SELECT DATEPART(isowk, myDate) AS Week_Num, DATEPART(yyyy, myDate) AS [Year], SUM(Sales) AS TotalSales

FROM @test-2

WHERE DATEPART(dw, myDate) IN (6,7) --Friday and Saturday Only

GROUP BY DATEPART(isowk, myDate), DATEPART(yyyy, myDate)

You can use whatever predicate you want based on your needs. I just used this example to demonstrate grouping up Fridays and Saturdays over multiple years.

SELECT quote FROM brain WHERE original = 1
0 rows returned

ps_vbdev SSCarpal Tunnel Points: 4060 More actions · Answer 4

many thanks guys ISOWEEK was spot on, never knew about that.

Jeff Moden SSC Guru Points: 1004356 More actions · Answer 5

ps_vbdev (5/26/2015)
many thanks guys ISOWEEK was spot on, never knew about that.

Thanks for the feedback. Just remember that some years have 52 weeks and some have 53. It's the nature of the year being 52.17 weeks long on average. For comparing the last week of each year, you might want to consider using the maximum week of the year.

--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.

Change is inevitable... Change for the better is not.

Helpful Links:
How to post code problems
How to Post Performance Problems
Create a Tally Function (fnTally)