Snowflake Schema

Synonyms

Snowflake join schema

Definition

Asnowflake schema has one “central” table whose primary key is compound, i.e., consisting of multiple attributes. Each one of these attributes is a foreign key to one of the remaining tables, which may, in turn, have some of its non-key attributes each be a foreign key to yet another, different table. This continues recursively with the remaining tables, until they are exhausted, forming chains or trees of foreign key dependencies rooted at the “central” table, i.e., each table in the schema (except the “central” table) is pointed to by exactly one such foreign key. (In the above, without loss of generality, we make the assumption that all tables except the “central” table have simple primary keys. This is usually the case in almost all practical situations, and as for efficiency, these keys are often generated, surrogate keys.)

Key Points

Many data warehouses (see definitional entry for “Data Warehouse”) that represent the multidimensional...