About Modeling Aggregates for Parent-Child Hierarchies

Fact tables in level-based hierarchies might only contain facts for a single level of the hierarchy.

Facts for higher-level dimension members can be calculated by aggregating the facts from the lower-level fact table or from a higher-level summary table.

In contrast, parent-child hierarchies require data modelers to make some additional decisions related to how to store the base facts in the fact table and how to aggregate the base facts to obtain the facts for higher-level members of the parent-child hierarchy.