What entity does the database source option NOT allow specifying constraints for?

In Mendix, when working with the database source option, you have the ability to set constraints for the primary entity, entities derived from associations, and all entities present in the database. However, when it comes to related entities, the database source does not allow direct specification of constraints like it does for the primary entity. This is because related entities are usually accessed through associations rather than being queried directly with specific constraints applied.

The primary entity allows for constraints to be defined to limit the records retrieved based on specified criteria. Similarly, entities derived from associations can have constraints, as these relationships are typically defined in a manner that allows for filtering relevant data according to particular logic.

The reason constraints cannot be set for any related entities directly is due to the nature of how data is structured and queried in Mendix, where such filters are usually couched within the context of the main entity or via associations. This reflects the design principles of Mendix, where the focus is on primary and associated data relationships to structure queries effectively.