If you want to create a table on one worksheet, and/or do a calculation that involves fields from two data sources, you need to either join or blend. This is because joining and blending are the two ways Tableau has of knowing how 2 data sources relate to each other.
If the fields are all totally the same and in the same data source, unioning might work well though: Union Your Data
which would basically combine the two data sources into one.
What is the reason you were trying to avoid joining or blending?
Thank you Amber.
The data is from a model ran every month so I am trying to compare previous month's model results to the current month's without blending the two but I guess I am going to have to blend the two.
Thanks once again, this is useful.
If I understand your issue you run a report every month and you would like to the results from that report and append it to the data from previous months reports so you can compare MOM values - in her response Amber has given you a link to do that by using Union (not blending) to append the data