Introduction
Early Data Management: File-Based Systems (1950s–1960s)
Characteristics
Key Features
- Data stored in flat files (text or binary)
- Programs written in COBOL, FORTRAN, or Assembly
- Tight coupling between programs and data
Limitations
- Data redundancy: Same data stored in multiple files
- Data inconsistency: Changes in one file not reflected in others
- Difficult data access: Required writing new programs
- Poor security and integrity
- Lack of concurrency control
These limitations highlighted the need for a more systematic approach to data management.
Hierarchical Database Model (1960s–1970s)
Overview
The hierarchical database model was one of the first database models introduced. Data was organized in a tree-like structure with parent-child relationships.
Example
IBM’s Information Management System (IMS) is a classic hierarchical database.
Characteristics
- One-to-many relationships
- Each child has only one parent
- Fast access for predefined queries
Advantages
- Simple structure
- Efficient for hierarchical data
Disadvantages
- Rigid structure
- Difficult to represent many-to-many relationships
- Complex data access paths
Network Database Model (1970s)
Overview
The network database model was developed to overcome the limitations of the hierarchical model.
Key Contribution
The CODASYL (Conference on Data Systems Languages) group formalized this model.
Characteristics
- Graph-like structure
- Many-to-many relationships
- Data connected through pointers
Advantages
- Greater flexibility than hierarchical model
- Reduced data redundancy
Disadvantages
- Complex design and maintenance
- Requires procedural navigation
- High programming complexity
Relational Database Model (1970s–1980s)
Origin
The relational model was proposed by Dr. E. F. Codd in 1970 at IBM.
Core Concepts
- Data stored in tables (relations)
- Rows (tuples) and columns (attributes)
- Use of keys and constraints
- Based on mathematical set theory and predicate logic
Advantages
- Data independence
- Simple and intuitive structure
- Powerful querying using SQL
- Reduced redundancy through normalization
Major Systems
- Oracle
- MySQL
- SQL Server
- PostgreSQL
- DB2
The relational model became the most widely adopted database model and remains dominant today.
Object-Oriented Databases (1980s–1990s)
Motivation
As object-oriented programming languages became popular, there was a need to store complex objects directly.
Features
- Data stored as objects
- Supports inheritance, encapsulation, and polymorphism
- Suitable for multimedia, CAD, and engineering applications
Limitations
- Lack of standard query language
- Limited commercial success
- Complexity compared to relational databases
Object-Relational Databases (1990s)
Hybrid Approach
Object-relational databases combine relational concepts with object-oriented features.
Features
- User-defined types
- Inheritance
- Complex data types (XML, JSON)
Examples
- PostgreSQL
- Oracle Object-Relational extensions
This model improved flexibility while retaining the reliability of relational databases.
NoSQL Databases (2000s–Present)
Background
The rise of big data, cloud computing, and web-scale applications led to the emergence of NoSQL databases.
Characteristics
- Schema-less or flexible schema
- Horizontal scalability
- High availability
Types of NoSQL Databases
- Key-Value Stores (Redis)
- Document Stores (MongoDB)
- Column-Family Stores (Cassandra)
- Graph Databases (Neo4j)
Use Cases
- Social networks
- Real-time analytics
- IoT systems
NewSQL and Modern Database Systems (2010s–Present)
NewSQL
NewSQL databases aim to combine:
- Scalability of NoSQL
- ACID properties of relational databases
Examples
- Google Spanner
- CockroachDB
Cloud-Native Databases
- Fully managed services
- Auto-scaling and fault tolerance
- Examples: Amazon Aurora, Azure SQL Database

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