Data Warehouse Dimensional Modeling-
We know that the large information is stored in data warehouse with different formations schema. It is nothing but the logical description of entire database system. The all database structure are represented with dimensional modelling in data warehousing, All data warehouse tables are related with each other for extracting information with user requirement. The all tables are sharing data from one another with use of primary key and foreign key. The all tables is indicated with Fact and dimension tables. That fact and dimension tables are represented the whole structure of data warehouse. In dimensional modelling the one fact table is join to another dimensional table for indicating sharing data. Dimensional modelling are designed for reading summarizing and analyzing information from large database.
Fact Table-
Fact table represent business main components or entities like sales,customer,product.
Dimension Table-
Dimension table contains the attribute of fact table that describe the extra information about fact table.
The data warehouse dimensional modelling are divided into-
- Star Schema
- Snowflake Schema
- Galaxy Schema
1. Star Schema-
Star schema is the model architecture of simplest data warehouse structure. In Star schema the fact table is located into center and all dimension table attached to fact table. The fact table represent the entities and dimension table represents extra information about that entities. It is easy to understand simple structure small number of table to join.
2. Snowflake Schema-
Snowflake is a very complex architecture of data warehouse. It is the extraction of star Schema in snowflake schema. The one fact table is attached to multiple dimension tables but each dimension table is split again and join to another dimension table for representing extra information about that dimension table.
3. Galaxy Schema-
In Galaxy schema multiple fact tables are present and that all fact tables are connected with each other for sharing information and all dimension tables are attached to fact table in Galaxy schema. Multiple fact table can access the information from 1 single dimension table.
