Data Engineering Technical Blog

When we think about dimensional modelling then two major and very important modeling schema comes into picture called the start schema and the snowflake schema. So lets go into details on start and snowflake schema. Star schema What is star schema? The star schema architecture is the simplest data warehouse schema. It is called a star schema because the diagram resembles a star, with points radiating from a center. The center of the star consists of fact table and the points of the star are the dimension tables. Usually the fact tables in a star schema are in third normal form(3NF) whereas dimensional tables are de-normalized. Despite the fact that the star schema is the simplest architecture, it is most commonly used nowadays and is recommended by Oracle . Snowflake schema What is snowflake schema? The snowflake schema architecture is a more complex variation of the star schema used in a data warehouse, because the tables which describe the dimensions ...

TYPES OF DIMENSIONS Conformed Dimension: Conformed dimensions mean the exact same thing with every possible fact table to which they are joined. Eg: The date dimension table connected to the sales facts is identical to the date dimension connected to the inventory facts. Junk Dimension: A junk dimension is a collection of random transactional codes flags and/or text attributes that are unrelated to any particular dimension. The junk dimension is simply a structure that provides a convenient place to store the junk attributes. Eg: Assume that we have a gender dimension and marital status dimension. In the fact table we need to maintain two keys referring to these dimensions. Instead of that create a junk dimension which has all the combinations of gender and marital status (cross join gender and marital status table and create a junk table). Now we can maintain only one key in the fact table. Degenerated Dimension: A degenerate dimension is a dimension whic...