what am i doing wrong here, as that is what i am doing?
Can you download & share the query profile please?
This may help: I found this error message when i went into jobs. do you know what it means?
Yes - make sure the join key columns are of the same data type. For example, if the join key is a number 1,2,3,4,5,etc you will get this error if 1 dataset in Dremio has that column of type Integer and another has the column as type Text. Just make sure the data types match across both datasets for the join keys. You can quickly change the data type by clicking the icon to the left of the column name.
if i change the data type in dremio there are no call backs to the actual database. It just changes the data type for that instance? What page would that be on, where i can change the data type of a field?
Everything you do in Dremio UI is in a virtualized context. When you save anything in the UI, it saves as a VDS (virtual dataset). We will still make call backs to the underlying db.
The page you are currently on in the screenshot above is where you go change the data type. You will likely have to start over > open just 1 table > change data type > save as VDS > repeat with another table > then join the 2 VDSs together into a final VDS (then eventually connect Tableau to the final VDS).