PostgreSQL

vs

IBM DB2

MariaDB is an free and open-source, community-developed relational database management system. MariaDB is a fork of MySQL, and is developed and maintained by the creators of MySQL, after concerns over its acquisition by Oracle Corporation in 2009. The databases comes bundled by default with most Linux distributions and is also apart of most cloud offerings. MariaDB is built upon the values of performance, stability, and openness which is ensured through the MariaDB Foundation.

The worlds most popular free open-source relational database, MySQL is used by 150,000 + companies across the globe. The relational database management system is released and distributed under the GPL license and openly developed by the community. MySQL uses SQL as its query language and is fully integrated and ACID compliant.

SQLite is a free and open-source relational database management system that implements a small, fast, self-contained, high-reliability, full-featured, SQL database engine. Rather than being a typical client–server database engine, SQLite is self-contained and can be embedded into applications. Making it perfect for development frameworks that want to provide a default database without setup, or applications that needs an embedded database. SQLite is built into all mobile operating systems and most computers and comes bundled with a countless applications. SQLite is also ACID-compliant and implements most of the SQL standard, generally following PostgreSQL syntax.

RethinkDB is a scalable, open-source database designed for real-time applications. When your app polls your database for data, it becomes slow, unscalable, and cumbersome to maintain. RethinkDB solves this by providing a new database access model, where developers can instruct the database to continuously push updated query results to their applications, without polling.

BigchainDB allows developers and enterprise to deploy blockchain proof-of-concepts, platforms and applications with a blockchain database, supporting a wide range of industries and use cases. BigchainDB provides high throughput, low latency, powerful query functionality, decentralized control, immutable data storage and built-in asset support, BigchainDB is like a database with blockchain characteristics.

NuoDB is a distributed relational database management system utilizing SQL. The database is architected to meet the rapidly evolving demands of today's enterprises, NuoDB can be used to deploy on-premise, extend to the cloud, scale on demand, eliminate downtime and reduce total cost of ownership. All while maintaining SQL compatibility and a workflow that most developers are familiar with.