How do relational databases differ from non-relational (NoSQL) databases?

Relational databases (RDBMS) and non-relational (NoSQL) databases differ in data model, storage method, and usage.

Relational databases:

• Store data in tables with a fixed schema (rows and columns).
• Use SQL for queries.
• Provide ACID properties (atomicity, consistency, isolation, durability).
• Well-suited for complex transactions and structured data.

Non-relational databases (NoSQL):

• Can store data as documents (JSON), key-value pairs, graphs, or columns.
• Usually do not require a fixed schema, offering flexibility.
• Often focused on scalability and high performance.
• May sacrifice some ACID properties for availability and scalability (e.g., eventual consistency).

Example:

• Relational DB: PostgreSQL, MySQL
• NoSQL: MongoDB (documents), Redis (key-value), Cassandra (columnar)

The choice depends on requirements for data structure, scalability, and consistency.