Databases are the backbone of modern software systems, storing and managing data across virtually every application domain. From traditional relational systems that power banking and e-commerce to specialized vector databases enabling AI applications, choosing the right database type directly impacts performance, scalability, and development velocity. Understanding the landscape—relational, NoSQL, NewSQL, specialized systems, and cloud-native platforms—is critical because each category optimizes for different trade-offs in consistency, availability, query capabilities, and operational complexity. In 2026, the boundary between categories continues to blur as most leading systems adopt multi-model capabilities and AI-native features.
What This Cheat Sheet Covers
This topic spans 19 focused tables and 109 indexed concepts. Below is a complete table-by-table outline of this topic, spanning foundational concepts through advanced details.
Table 1: Relational Databases (RDBMS)
| Database | Example | Description |
|---|---|---|
SELECT * FROM employees WHERE dept_id = 10 | • Enterprise-grade RDBMS with advanced features like partitioning, RAC clustering, and comprehensive PL/SQL support • dominant in large organizations. | |
CREATE TABLE users (id INT PRIMARY KEY, name VARCHAR(100)) | • World's most popular open-source RDBMS • known for ease of use, replication, and widespread community support across web applications. | |
SELECT jsonb_column->>'key' FROM table WHERE id = 1 | • Most advanced open-source RDBMS • supports JSONB, full-text search, advanced indexing, and extensibility via custom types and functions. |