You can use Tableau’s inbuilt pivot method as below, without reshaping in source .
- CTRL Select all 3 dimensions you want to merge , and click on pivot .
- You will get your new reshaped data as below, delete other columns :
- Finally build your view.
I hope this answers .Rest other options for the above results include JOIN at DB level, or creating multiple calculated fields for each attribute value which are not scalable.