When a hierarchical relationship in a dimension table is normalized, low-cardinality attributes appear as secondary tables connected to the base dimension table by an attribute key. When this process is repeated with all the dimension table’s hierarchies, a characteristic multilevel structure is created that is called a snowﬂake. Although the snowﬂake represents hierarchical data accurately, you should avoid snowﬂakes because it is difficult for business users to understand and navigate snowﬂakes. They can also negatively impact query performance. A ﬂattened denormalized dimension table contains exactly the same information as a snowﬂaked dimension.