SQL vs NoSQL Databases: A Concise Comparison for System Design

SQL databases (Relational) organize data in static tables with strictly structured schemas and foreign key relationships. NoSQL databases (Non-relational) store data dynamically as key-value pairs, document collections, wide-columns, or graphs.

• Schema: SQL requires pre-defined structural DDL. NoSQL schemas are dynamic and polymorphic. • Scaling: SQL scales vertically by default. NoSQL scales horizontally via partitioning and sharding naturally. • Transactions: SQL natively guarantees ACID compliance. NoSQL focuses on BASE models (Basically Available, Soft State, Eventual Consistency). Review these tradeoffs in the CAP Theorem guide.