Concept
SQL vs NoSQL: Core Structural Differences
Choosing the correct database architecture depends on the structure of your data and application query patterns:
| Feature | SQL (Relational, e.g., PostgreSQL) | NoSQL (Document-based, e.g., MongoDB) |
|---|---|---|
| Data Model | Tabular (Rows and Columns, rigid schemas). | Hierarchical (JSON/BSON documents, flexible). |
| Joins | Native and highly optimized (JOIN queries). | Application-level or costly aggregation $lookup. |
| Transactions | Strong ACID compliance across all tables. | Atomic single-document writes; replica transactions. |
| Scalability | Vertical scale (more RAM/CPU) primarily. | Horizontal scale (sharding across clusters) natively. |
| Data Integrity | Strict constraints (FKs, Unique, Check). | Schema-less by default; verified at ODM/App level. |
The CAP Theorem
When scaling distributed databases, the CAP Theorem dictates that a system can only guarantee two out of three properties: