Having established a foundation in relational databases and SQL, we now turn our attention to different approaches for managing data. While the relational model is effective for structured data, certain scenarios involving large scale, high velocity, or less structured information benefit from alternative solutions.

This chapter introduces the concept of NoSQL databases. We will discuss the reasons behind their development and their general characteristics. You will learn about several prominent types of NoSQL databases, including:

• Document Databases: Storing data in flexible, document-like structures.
• Key-Value Stores: Simple models optimized for fast lookups based on a unique key.
• Column-Family Stores: Organizing data by columns rather than rows.
• Graph Databases: Designed specifically for managing highly interconnected data.

Finally, we will briefly compare the fundamental differences between SQL and NoSQL approaches to data storage and retrieval.