Hi Adam,
May be I have not understood your scenario.
However you want to show all the cases and just one record per material you have to preaggregate your material dimension data to store a single record per material with a concatenated string of all the case number of all the materials. There is no special functions available in HANA to achieve this on the fly however you can create procedure and loop to pre aggregate it into another table.
Refer http://scn.sap.com/thread/3294829 how to concatenate column values across row.Once you built your pre aggregated table just create the calculation view using the new table instead.
Hope this helps.
Thanks!!
Durga