UPDATE (2011-07-20): Indeed, with the release of CTP3 of SQL Server Denali we can order the dimension members by another column effectively making this post obsolete. Please ignore the advice below if you are working with a version of PowerPivot and BISM >= Denali CTP3.
I am sure that this post will get outdated very soon, but until that happens it is a neat little trick that PowerPivot users may need to know.
While in Analysis Services we can order our attribute hierarchies any way we want, in PowerPivot we are stuck with the default sort order, which can be annoying in some cases. The other day while building a PowerPivot model (which performed GREAT by the way), I had to order a band dimension, which had members like “Band 1-4”, “Band 5-10”, “Band 11-14”, “Band 15-19”,…, “Band 100-109”, etc. Alphabetically this got ordered very wrong as all bands starting with “Band 1…” got bunched up in the beginning followed by “Band 2…” The users were very unhappy and after searching for a solution I got a bit disheartened because I could not find a solution anywhere online.
The following is Adventure Works 2008 in Excel 2010 (through PowerPivot) and the default ordering of the English Month Name attribute in the Date dimension:
What I noticed was that the actual order which I wanted was reflected by the primary key of the table, which went 1,2,3,4,… So, I un-hid the key from the Pivot Table, renamed it to Band Order and showed users how they can nest it in front of the Band attribute. Because I had one key per band I did not have to worry about having multiple unordered bands under the order attribute.
Furthermore, if placed on columns, the Order attribute row can be hidden for sheets which remain static (it’s ok if they have slicers):
Otherwise, if it is on rows, we can use the Classic Pivot Table view and then hide the order column, which gives a different, but equally useful result:
As a side note, when ordering date attributes like in my examples above, you can use the Sort Options -> More Options functionality in Excel like described in a PowerPivot Team’s post. I used the month as an example and the technique described here should be used when having trouble with other attributes. You can also sort them manually by dragging and dropping them in the pivot table as Dan English explains here.