Hierarchies are mainly used in OBIA to drill down and up through the OBIEE reports.
For example Year, Quarter, and Month are all part of the Hierarchy.
Corresponding to each record in the dimension table we have one record in the Hierarchy table. This allows the user to drill down and drill up.
Mainly there are two types of Hierarchies
- Structured Hierarchy:These hierarchies have parent child relationship and are easy to model where each child has a fixed number of parents and a child cannot be a parent
- Unstructured Hierarchy:These hierarchies have unstructured parent-child relationships and these are difficult to model