This will have to be done before the data is read in Tableau. This might be a good one to add to the Ideas section!
you can't merge them but you could create a calculated dimension.
ex. you have two dimensions [city] and [village] where they have eithe ra valid name or are null
create a calculated field then use this:
if ISNULL( [city]) then village else city end then name it something like townname
now you can use this dimension in place of city and it should contain all the names.
- workbook attached as an example
city and village.twbx.zip 31.9 KB
Thanks - I don't know why that was so tricky for me to figure out.
How to do this when I have more than 2 dimensions?
If you mean to use more than 2 dimension to get a better and more accurate numbers with less unknowns/nulls, then you can drop each dimension to rows and see where you have unknowns that can be filled with previous dimension. Then create a calculated field to get one combined dimension that will consider all your dimensions. See this link that may help you: Combining two dimensions to get normalized data