Relational Databases (SQL)

Relational databases are structured around tables, rows, and columns. Each table is a collection of related data entries, and each entry is organized as a row with specific columns. This structured approach makes it easy to manage and query data using SQL (Structured Query Language).

Example: Imagine a simple database for a bookstore:

Table: Books

SQL Query:

SELECT title, author FROM Books WHERE price < 10.00;

NoSQL Databases

NoSQL databases offer a more flexible approach, using documents, collections, and fields. This makes them ideal for unstructured or semi-structured data. NoSQL databases can store data in various formats, including JSON, making them highly adaptable to different types of data and use cases.

Example: Here’s a similar example using a document-based NoSQL database (like MongoDB):

Collection: Books

[
  {
    "id": 1,
    "title": "The Great Gatsby",
    "author": "F. Scott",
    "price": 10.99
  },
  {
    "id": 2,
    "title": "1984",
    "author": "George Orwell",
    "price": 8.99
  }
]

NoSQL Query (MongoDB):

db.Books.find({ price: { $lt: 10.00 } }, { title: "1, author: 1 });"

Popular Databases

Relational Databases:

• MySQL: Widely used for web applications and known for its speed and reliability.
• PostgreSQL: Praised for its advanced features and compliance with SQL standards.
• Oracle Database: A robust option for large enterprises with complex requirements.
• SQL Server: Integrates well with other Microsoft products and is popular in enterprise environments.

NoSQL Databases:

• MongoDB: A leading document-based database, great for handling JSON-like documents.
• Redis: A key-value store known for its speed and used for caching and real-time analytics.
• Apache Cassandra: A column-family store that's highly scalable, perfect for big data applications.
• Neo4j: A graph database that's ideal for data with complex relationships, like social networks.