What is Galaxy Schema?
A galaxy schema (also known as a fact constellation schema) is a data modeling technique where multiple fact tables share common dimension tables.
- It contains more than one fact table
- These fact tables are connected to shared dimension tables
- The structure looks complex, like a galaxy of stars
That’s why it is called Galaxy Schema.
In Simple Terms
Galaxy Schema = Multiple fact tables + shared dimension tables
Example
Fact Tables:
- Sales
- Orders
- Inventory
- Product
- Customer
- Date
- Region
Why it is Used
- To handle multiple business processes
- To integrate data from different departments
- To build enterprise-level data models
Features of Galaxy Schema
1. Multiple Fact Tables
Unlike Star Schema, it contains multiple fact tables representing different processes.
2. Shared Dimension Tables
Dimension tables like Product, Customer, and Date are shared across fact tables.
3. Complex Structure
The model is more complex due to:
- Multiple relationships
- Multiple fact tables
4. Scalable Design
You can easily:
- Add new fact tables
- Expand the model for new business needs
5. Supports Advanced Analytics
Useful for analyzing data across:
- Sales
- Inventory
- Orders
Merits of Galaxy Schema
1. Handles Multiple Processes
Supports multiple business operations in a single model.
2. Reusable Dimensions
Common dimension tables can be reused, reducing duplication.
3. Scalable and Flexible
Easy to expand by adding new fact tables.
4. Better Enterprise Modeling
Ideal for large organizations with complex data needs.
Demerits of Galaxy Schema
1. High Complexity
- Difficult to design and maintain
- Requires strong data modeling knowledge
2. Performance Challenges
- Multiple joins may slow down queries
3. Hard for Beginners
- Not easy to understand for non-technical users
4. Requires Careful Relationship Management
Incorrect relationships can lead to wrong analysis.
