a Describe the concept and purpose of the star schema What d

a. Describe the concept and purpose of the star schema. What does a Fact represent in a star schema? What do Dimensions represent in a start schema?

Solution

Star schema:

The star schema architecture is the easiest data warehouse schema. It is called a star schema because the diagram resembles a star, with points radiating from a center. The middle of the star consists of fact table and the points of the star are the dimension tables. Typically the fact tables in a star schema are in third normal form whereas dimensional tables are denormalized. Although the fact that the star schema is the simplest architecture, it is mainly used nowadays

Fact represent in a star schema:

A fact table typically has two types of columns: foreign keys to dimension tables and measures those that hold numeric facts. A fact table can have fact\'s data on detail or aggregated stage.

Dimensions represent in a start schema:

A dimension is a structure usually collected of one or more hierarchies that categorizes information. If a dimension hasn\'t got a hierarchies and levels it is called flat dimension. The primary keys of every dimension tables are piece of the composite primary key of the fact table. Dimensional attributes help to describe the dimensional value. They are normally descriptive, textual values. Dimension tables are commonly tiny in size then fact table.

Typical fact tables store data about sales while dimension tables data about geographic region (markets, cities) , clients, products, times, channels.

The main qualities of star schema: