How do structured relational databases differ from non-relational solutions?

Relational databases (SQL) use a structured schema with tables, rows, and columns, where data is linked through keys. They support complex queries using SQL language and ensure transactional integrity and data consistency.

Non-relational databases (NoSQL) do not require a fixed schema and can store data as documents, key-value pairs, graphs, or columns. They are more flexible and scalable, often used for large volumes of data and distributed systems, but may not support complex transactions.

Examples of differences:

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

The choice depends on data structure requirements, scalability, and operation types.