I know there are many questions on data blending but I have not found a resource that would help this completely click with me. The second reason I am asking is because I work somewhere where there are individual tables as datasources that live on Tableau Server, and I can't join them, so naturally I feel like the best course of action is to create a new datasource that DOES join them.
Attached is a workbook with three sheets and a dashboard. There are two simple data sources that join on Id. The idea was that the first thing someone would filter on is something that only exists in Datasource 1 (there is a hierarchy of sorts from Territory->ID in this case), so naturally I felt that I should make it my primary data source. The other reason for doing so is that if I don't, I will have NULL in the Territory filter, and I do not know the best way to solve for that. Create a duplicated Territory, filter that one for Non-NULLs, then use the second one? The second datasource has a numeric field that I want to bucket. There is a natural join here, but I cannot do that if both datasources are Tableau Server data sources. My questions are as follows:
a) If I set Sheet 1 to be filtered on Territory and ID (and make ID only filter relevant values, in an attempt to make a cascading filter), and I then use apply the "use on other worksheets" to make the ID column as a filter for the Sheet 2 (that still retains the Datasource 1 as the Primary), why does the Sheet 2 on the Dashboard not filter down to the narrowed down IDs, regardless of whether I use the ID column from the Primary source or the secondary source? Does it negate the Territory filter that does not exist on Sheet 2?
b) If I make a calculated field for Datasource 2, and I set this to be a filter on Sheet 1, it seems to work...but why can I not use this filter on Sheet 3 when the Datasource 2 is now the primary data source? Is it because no relationship exists on this field? I don't see why that would matter, and I would like to know more.
c) For Sheet 2, even if everything visible is from the secondary datasource, I will still get asterisks. I guess I felt like if everything was on one datasource, it could keep the granularity. Does this automatically go out the window if a secondary datasource is being used?
d) I always see the same application for data blending. The tutorials are always "coffee store 1" and "coffee store 2" so it just feels like this is a "fake union" of sorts. Maybe there is a quota application that could be useful (one file has attainment, the other quota per person). But even still, I feel like I would union these and have an identifier to separate them. I almost feel like if blending is avoidable, do it. Is that bad advice?
e) If joining is the way to go, what sort of best practices are used in an organization with respect to publishing datasources? I get the feeling that people would just make all kinds of datasources if they could. For example, I have something that relies on two tables and maybe 8 columns. I feel like that could be its own datasource, it is very lean and probably easily refreshable. But then if someone has a slightly different request, do people just make one with 9 columns? It doesn't seem like Tableau is good at "ingest this database x and retain the PK/FK relationships", but I don't know enough to have an informed opinion.
I apologize if this wasn't explained well or if it gets asked a lot, but I haven't really come across something that explains this concept in a way that makes perfect sense to me and I thought maybe making my own example would help me understand.
blendjointest.twbx 45.1 KB