Logical database design and physical database design are two distinct phases in the database design process, each focusing on different aspects of the database structure.
Logical Database Design
The logical database design focuses on the data itself and how it is organized and related. It defines the entities, attributes, and relationships between them, without considering the specific implementation details.
- Focus: Data structure and relationships
- Outcome: Entity-Relationship Diagram (ERD)
- Example: Defining an entity called "Customer" with attributes like "Name," "Address," and "Phone Number," and establishing a relationship between "Customer" and "Order" entities.
Physical Database Design
The physical database design takes the logical design as input and translates it into a concrete implementation. It considers the specific database management system (DBMS) and hardware environment to optimize performance and efficiency.
- Focus: Database storage, indexing, and access methods
- Outcome: Database schema, tables, indexes, and storage structures
- Example: Choosing a specific data type for the "Phone Number" attribute, creating indexes to speed up searches, and selecting an appropriate storage structure for the "Order" table.
Key Differences
| Feature | Logical Database Design | Physical Database Design |
|---|---|---|
| Focus | Data structure and relationships | Database implementation and optimization |
| Outcome | Entity-Relationship Diagram (ERD) | Database schema, tables, indexes, and storage structures |
| Level of Detail | High-level, abstract | Low-level, specific |
| Dependencies | Independent of specific DBMS | Dependent on chosen DBMS |
| Implementation | Conceptual, not directly implemented | Concrete, implemented in a database |
In Summary
Logical database design focuses on the data model, while physical database design maps that model to a specific database implementation. The logical design ensures the integrity and accuracy of the data, while the physical design optimizes the performance and efficiency of the database.
