What is the typical relationship between levels in a dimension hierarchy from top to bottom?

The typical relationship between levels in a dimension hierarchy from top to bottom is characterized as a one to many relationship. This means that at each hierarchical level, a single parent level can relate to multiple children levels. For example, consider a time hierarchy where the top level is "Year," and the middle level is "Month." One year can include many months, thereby establishing a one to many relationship. Similarly, within a geography hierarchy, a continent may contain several countries, again reflecting the same relationship.

This structure allows for effective organization and querying of data in a database or data warehouse context, where each level can contain a number of lower-level entities. This simple and clear relationship is fundamental in maintaining the integrity of the data hierarchy and in enabling accurate data analysis.

Other relationship types, such as many to many relationships or characteristics like zero cardinality, do not typically apply in this scenario. Many to many relationships imply that multiple records at one level can relate to multiple records at another level, which does not generally align with how dimension hierarchies are structured. Zero cardinality suggests the absence of any relationship, which contradicts the essential purpose of hierarchies in organizing data meaningfully.