About the Implicit Fact Column
For each subject area in the presentation layer, you can set an implicit fact column.
The subject area's specified implicit fact column is added to a query when it contains columns from two or more dimension tables and no measures. The column isn't visible in the results. It's used to specify a default join path between dimension tables when there are several possible alternatives or contexts.
If an implicit fact isn't configured, then the Oracle Analytics query engine uses any fact table source to answer dimension-only subrequest that contains multiple dimensional references but no fact reference.
The Oracle Analytics query engine can also use any fact table source if the configured implicit fact column isn't relevant to the dimensions that are joined. This could happen, for example, when implicit fact column is a level based measure at a level higher than the dimensional only subrequest.
You use the Implicit Fact Column field in the subject area's General tab to add, remove, or replace the implicit fact column.