Sample Table:
id     aff1    aff2    aff3    value
1       a        x      b        5
2       b        c      x        4
3       a        b      g        1
What I want?
Aggregate the aff columns to calculate the sum of "value" for each aff. 
For example, the above aggregation should result to:
aff    sum
a       6
b       10
c       4
g       1
x       9
Ideally, I want to do this directly in tableau without remaking the table by unfolding it along all the aff columns.