Data Warehouse: Snowflake Schema

Snowflake Schema
In data warehouse, a snowflake schema is a logical arrangement of tables in a multidimensional database such that the entity relationship diagram resembles a snowflake in shape. The snowflake schema is represented by centralized fact tables which are connected to multiple dimensions.

It is similar to the star schema. However, in the snowflake schema, dimensions are normalized into multiple related tables, whereas the star schema's dimensions are normalized with each dimension represented by a single table.

Example:Snowflake schema used by example query.

SELECT
        B.Brand,
        G.Country,
        SUM(F.Units_Sold)
FROM Fact_Sales F
INNER JOIN Dim_Date D             ON F.Date_Id = D.Id
INNER JOIN Dim_Store S            ON F.Store_Id = S.Id
INNER JOIN Dim_Geography G        ON S.Geography_Id = G.Id
INNER JOIN Dim_Product P          ON F.Product_Id = P.Id
INNER JOIN Dim_Brand B            ON P.Brand_Id = B.Id
INNER JOIN Dim_Product_Category C ON P.Product_Category_Id = C.Id
WHERE
        D.YEAR = 1997 AND
        C.Product_Category = 'tv'
GROUP BY
        B.Brand,
        G.Country

Read more: http://en.wikipedia.org/wiki/Snowflake_schema