Tell me about SQL and NoSQL databases

SQL databases (relational) are based on tables with a clearly defined schema, support complex queries using SQL language, transactions, and ensure data integrity. Examples: PostgreSQL, MySQL.

NoSQL databases are non-relational stores that can be document-based, key-value, graph, or column-oriented. They are more flexible in terms of schema, often scale better horizontally, and are suitable for large volumes of unstructured data. Examples: MongoDB (document), Redis (key-value).

The choice between them depends on requirements for data structure, scalability, consistency, and the type of workload.