O'Reilly Answers: What is new trends of database system?

Database Internals

Alex Petrov

CockroachDB: The Definitive Guide

Guy Harrison, Jesse Seldess, and Ben Darnell

The NoSQL Movement

Between 2008 and 2010, dozens of new database systems emerged, all of which abandoned the three pillars of the RDBMS: the relational data model, SQL language, and ACID transactions. Some of these new systems—Cassandra, Riak, Project Voldemort, and HBase, for example—were directly influenced by nonrelational technologies developed at Amazon and Google.

Many of these systems were essentially “schema-free”—supporting or even requiring no specific structure for the data they stored. In particular, in key-value databases, an arbitrary key provides programmatic access to an arbitrary structured “value.” The database knows nothing about what is in this value. From the database’s view, the value is just a set of unstructured bits. Other nonrelational systems represented data in semi-tabular formats or as JSON (JavaScript Object Notation) documents. However, none of these new databases implemented the principles of the relational model.

These systems were initially referred to as distributed nonrelational database systems (DNRDBMSs), but—because they did not include the SQL language—rapidly became known by the far catchier term “NoSQL” databases.

NoSQL was always a questionable term. It defined what the class of systems discarded, rather than their unique distinguishing features. Nevertheless, “NoSQL” stuck, and in the following decade, NoSQL databases such as Cassandra, DynamoDB, and MongoDB became established as a distinct and important segment of the database landscape.