snowflake schema
A snowflake schema is a special form of an entity relations diagram( ERD). It is used to represent multidimensional structures in databases and forms an extension of the Star schema.
The name Snowflake Schema (the German translation Schneeflocken-Schema is not in use) is derived from its graphical form. In a snowflake schema, there is always a central fact table surrounded by several dimension tables.
In contrast to the Star schema, where the surrounding dimension tables are all directly linked to the fact table, in the Snowflake schema there are several levels, e.g. the fact table "Production" is linked to the dimension table "Location". The latter is in turn connected to the table "Country", which has no direct connection to "Production". In this way, hierarchical structures can be normalized. For this reason, snowflake schemas are mainly found in central data warehouse databases. Star schemas, on the other hand, tend to occur more in data marts.