cross table and calculated field

Question

I'm just starting using Powerpivot, and my first application raised some harder problems that I would have thought... Here is my problem:

I have 3 tables: factRepairs; factCorss; dimSpares

factRepairs:

factCross

dimSpares

factRepairs is linked to factCross by a relationship between the Repair column, and factCross is linked to dimSpares through Spare ID <->Spare

I want to add a calculated column (or measure, not sure at this stage) to give the cost of spares used for one repair.

I've been looking for solution for a while but I didn't manage to figure it out... If someone can guide me through a formula to do this it would be greatly appreciated!

Thanks,

Answer 1

You are right to think that many-to-many is an non-trivial problem in PowerPivot!

The good news is that this is probably more of a data structure issue than a pure underlying many to many situation and can be easily solved with a calculated column on the factCross table. This works a bit like a SUMIF in excel and doesn't require a relationship:

 = CALCULATE(SUM(dimSpares[price]), 
       FILTER(dimSpares, 
              dimSpares[id] = EARLIER([spare id])
              )
             )

You can then write a measure/calculated field to sum the cost and if you create a relationship between factRepairs and factCross you should be in business.

If you are looking for a more sophisticated way to deal with these problems then try the Many to Many revolution but honestly that's about as complex as DAX gets so I would concentrate on simpler stuff :-)