Non-relational databases

Non-relational databases, store unstructured or semi-structured data. They don't use tables with columns and rows the way that relational databases do. Instead, they use a storage model that's optimized for the specific requirements of the type of data being stored. Non-relational databases allow for larger sets of distributed data to be accessed, updated, and analyzed quickly.

Examples of non-relational databases include MongoDB, Azure Cosmos DB, DocumentDB, Cassandra, Couchbase, HBase, Redis, and Neo4j.

Some non-relational databases are referred to as NoSQL databases. NoSQL refers to data stores that use no SQL or not only SQL for queries. Instead, NoSQL databases use other programming languages and constructs to query the data. Many NoSQL databases do support SQL-compatible queries, but the way that they execute these queries is usually different from the way a traditional relational database would execute the same SQL query.

One type of non-relational database—an object database—uses object-oriented programming. Objects are encoded with a state (factual data) that's stored in a field or variable and a behavior that's displayed through a method or function. Objects can be held in persistent storage forever and read and mapped directly without an API or tool, which yields faster access to data and better performance. However, object databases aren't as popular as other database types and can be challenging to support.