The Relational Model is the most popular and widely used data model in Database Management Systems. It represents data in the form of tables, making it easy to store, access, and manage information efficiently.
What is the Relational Model?
The relational model organizes data into relations, commonly known as tables. Each table consists of rows and columns, where:
- Rows represent records (tuples)
- Columns represent attributes (fields)
Each table represents a real-world entity.
Basic Terminologies
- Relation – A table in a database
- Tuple – A row in a table
- Attribute – A column in a table
- Domain – Set of allowed values for an attribute
- Degree – Number of attributes in a table
- Cardinality – Number of rows in a table
Keys in Relational Model
Keys play a vital role in uniquely identifying records and establishing relationships.
Types of Keys
- Primary Key – Uniquely identifies each record
- Candidate Key – Possible primary keys
- Alternate Key – Candidate keys not chosen as primary
- Foreign Key – Links one table to another
- Composite Key – Combination of multiple attributes
Integrity Constraints
Integrity constraints ensure accuracy and consistency of data.
- Domain Constraint – Values must belong to a valid domain
- Entity Integrity – Primary key cannot be NULL
- Referential Integrity – Foreign key must match a primary key
Relationships in Relational Model
Relationships between tables are created using foreign keys.
Types of relationships:
- One-to-One
- One-to-Many
- Many-to-Many
Many-to-many relationships are usually resolved using junction tables.
Advantages of Relational Model
- Simple and easy to understand
- Strong data integrity
- Flexible structure
- Supports powerful SQL queries
- Easy to modify and scale
Limitations of Relational Model
- Not suitable for highly complex data
- Performance issues with very large datasets
- Requires normalization to reduce redundancy
Relational Schema
A relational schema defines the structure of tables including:
- Table name
- Attributes
- Primary keys
- Foreign keys
Example:
Student (Student_ID, Name, Course_ID)
Conclusion
The relational model provides a structured and reliable way to store data in a database. Its simplicity, flexibility, and strong data integrity make it the backbone of modern database systems. Understanding this model is essential for working with SQL and designing efficient databases.