When is an association in a CDS view entity translated into a join on the database level?

The correct answer highlights that an association in a Core Data Services (CDS) view entity is translated into a join at the database level when it is used in a path expression. This means that until the association is actually leveraged in a way that requires data to be fetched together, no join is instantiated in the underlying SQL.

Associations in CDS views help maintain a relationship between entities, but they are not immediately translated into database joins until they are utilized. This allows for more flexibility and efficiency, as not every defined association will necessarily require data from related tables unless explicitly invoked through an expression or condition.

When associations are defined, they create a conceptual link but do not inherently generate database-level joins. The joins are realized when the associations are actually queried, particularly in path expressions where data from both the main entity and its associated entities are needed. This strategic delay in the translation allows for optimized queries depending on the required data set.

In other contexts, merely defining the association or adding it to the element list does not trigger any join’s creation. Even during the view's activation phase, unless the association is called in a way that necessitates its use, there won't be a corresponding join. This design promotes efficient data retrieval by only joining tables when necessary