A hierarchy is a cascaded series of many-to-one relationships and consists of different levels.
Example, a region hierarchy is defined with the levels Region, State, and City.
Types of Hierarchies
1. Balanced hierarchy
2. Unbalanced hierarchy
3. Ragged hierarchy
1. Balanced hierarchy
A balanced hierarchy is one in which all of the dimension branches have the same number of levels. In other words, the branches have a consistent depth. The logical parent of a level is directly above it.
A balanced hierarchy can represent a date where the meaning and depth of each level, such as Year, Quarter, and Month, are consistent.
2. Unbalanced hierarchy
A hierarchy is unbalanced if it has dimension branches containing varying numbers of levels.
An unbalanced hierarchy has levels that have a consistent parent-child relationship, but have a logically inconsistent level. The hierarchy branches also can have inconsistent depths. An unbalanced hierarchy can represent an organization chart.
3. Ragged hierarchy
A ragged dimension contains at least one member whose parent belongs to a hierarchy that is more than one level above the child. Ragged dimensions, therefore, contain branches with varying depths.
A ragged hierarchy is one in which each level has a consistent meaning, but the branches have inconsistent depths.
A ragged hierarchy can represent a geographic hierarchy in which the meaning of each level, such as city or country, is used consistently, but the depth of the hierarchy varies.
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