What are the main differences between relational and non-relational databases?

Main differences between relational (SQL) and non-relational (NoSQL) databases:

• Data structure:

  • Relational databases store data in tables with a fixed schema (rows and columns).
  • Non-relational databases can store data as documents, key-value pairs, graphs, or columns, often without a strict schema.

• Query language:

  • Relational databases use SQL for complex queries and joins.
  • Non-relational databases often have their own APIs or query languages, which are simpler or specialized.

• Scalability:

  • Relational databases typically scale vertically (adding resources to a single server).
  • Non-relational databases are better suited for horizontal scaling (adding more servers).

• Transactions and consistency:

  • Relational databases support ACID transactions.
  • Non-relational databases may sacrifice strict consistency for performance and scalability (BASE).

Example: MySQL is relational, MongoDB is document-oriented NoSQL.