Database systems can be broadly categorized into relational (SQL-based) and nonrelational (NoSQL) models. Each approach offers distinct advantages and limitations that make them suitable for different use cases.

Relational Models

Relational databases organize data into tables with rows and columns, establishing relationships between tables through keys.

Key characteristics:

• Structured schema with predefined relationships
• ACID compliance (Atomicity, Consistency, Isolation, Durability)
• SQL as the standard query language
• Strong data integrity through foreign key constraints
• Examples: MySQL, PostgreSQL, Oracle, SQL Server

Nonrelational (NoSQL) Models

NoSQL databases provide flexible schemas for storing unstructured or semi-structured data, with various data models for different scenarios.

Main types of NoSQL databases:

• Document stores: Store data in JSON-like documents (MongoDB, CouchDB)
• Key-value stores: Simple key-value pairs for high-speed access (Redis, DynamoDB)
• Column-family stores: Store data in column families (Cassandra, HBase)
• Graph databases: Represent and store data as nodes and relationships (Neo4j, Amazon Neptune)

Comparison Table