About Right vs Left Join Behavior
The default behavior is to filter out the fact data rows that do not have a matching entry in the dimension. In SQL, this is referred to as right join behavior, meaning the dimension dataset is used as the basis of comparison when combining data from multiple tables in the connected data warehouse.
For example, if this Sales fact dataset was being joined to this Customer dimension, then only customers A, B, and C would be in the result (customer D would be excluded because it has no matching entry in the dimension dataset).
AtScale cubes do not support left join type relationships at this time.