Elements of Dimensional Data Model
Facts
Facts are the measurable data elements that represent the business metrics of interest. For example, in a sales data warehouse, the facts might include sales revenue, units sold, and profit margins. Each fact is associated with one or more dimensions, creating a relationship between the fact and the descriptive data.
Dimension
Dimensions are the descriptive data elements that are used to categorize or classify the data. For example, in a sales data warehouse, the dimensions might include product, customer, time, and location. Each dimension is made up of a set of attributes that describe the dimension. For example, the product dimension might include attributes such as product name, product category, and product price.
Attributes
Characteristics of dimension in data modeling are known as characteristics. These are used to filter, search facts, etc. For a dimension of location, attributes can be State, Country, Zipcode, etc.
Fact Table
In a dimensional data model, the fact table is the central table that contains the measures or metrics of interest, surrounded by the dimension tables that describe the attributes of the measures. The dimension tables are related to the fact table through foreign key relationships
Dimension Table
Dimensions of a fact are mentioned by the dimension table and they are basically joined by a foreign key. Dimension tables are simply de-normalized tables. The dimensions can be having one or more relationships.
Dimensional Data Modeling
Popular Schema – Star Schema, Snow Flake Schema
Dimensional Data Modeling is one of the data modeling techniques used in data warehouse design. The concept of Dimensional Modeling was developed by Ralph Kimball which is comprised of facts and dimension tables. Since the main goal of this modeling is to improve the data retrieval so it is optimized for SELECT OPERATION. The advantage of using this model is that we can store data in such a way that it is easier to store and retrieve the data once stored in a data warehouse. The dimensional model is the data model used by many OLAP systems.