TiDB - Distributed NewSQL database compatible with MySQL protocol

•    Go

TiDB is a distributed SQL database. Inspired by the design of Google F1 and Google Spanner, TiDB supports the best features of both traditional RDBMS and NoSQL. It is horizontally scalable, grow TiDB as your business grows. You can increase the capacity simply by adding more machines.

LEAP RDBMS

•    C

LEAP is an RDBMS (Relational Database Management System) implementing the relational Algebra - a core part of relational database theory. It is primarily used as an educational tool, but has found some novel uses and applications.

CUBRID - RDBMS Optimized for Web

•    C++

CUBRID is a relational database management system highly optimized for Web Applications, especially when complex web services process large amount of data and generate huge concurrent requests. CUBRID is being developed in C/C++. Includes HA, online incremental backup, Replication, Load balancing, Sharding, Caching and other features. It supports JDBC, PHP, ODBC/.NET, Ruby & Python APIs.

ActorDB - Distributed SQL database with linear scalability

•    Erlang

ActorDB is ideal as a server side database for apps. Think of running a large mail service, dropbox, evernote, etc. They all require server side storage for user data, but the vast majority of queries is within a specific user. With many users, the server side database can get very large. Using ActorDB you can keep a full relational database for every user and not be forced into painful scaling strategies that require you to throw away everything that makes relational databases good.

PostgreSQL - Powerful, Open Source Object-Relational Database System

•    C

PostgreSQL is a powerful, open source object-relational database system. It has more than 15 years of active development and a proven architecture that has earned it a strong reputation for reliability, data integrity, and correctness. It is fully ACID compliant, has full support for foreign keys, joins, views, triggers, and stored procedures (in multiple languages). It has native programming interfaces for most of the programming language.

SchemaCrawler

SchemaCrawler is an open-source Java API that makes working with database metadata as easy as working with plain old Java objects. SchemaCrawler is also a database schema discovery and comprehension, and schema documentation tool. You can search for database schema objects using regular expressions, and output the schema and data in a readable text format, and find potential design issues with lint . The output is designed to be diff-ed against other database schemas. SchemaCrawler support

EventQL - The database for large-scale event analytics

•    C++

EventQL is a distributed, column-oriented database built for large-scale event collection and analytics. It runs super-fast SQL and MapReduce queries. Its features include Automatic partitioning, Columnar storage, Standard SQL support, Scales to petabytes, Timeseries and relational data, Fast range scans and lot more.

Daffodil DB- One$DB, a Java RDBMS

•    Java

One$DB is Open Source version of Daffodil DB, a commercial Java Database. It is standards based, platform independent RDBMS that can be embedded into any application with minimal administration. One$DB is available in both Embedded and Network editions.

rc21 RDBMS

•    C++

rc21 is a c++ class library for relational database operations, an embeddable library, an RDBMS server, an ODBC interface, and several command-line and MS-Windows-based utilities.

LucidDB - RDBMS built entirely for Data Warehousing and Business Intelligence

•    Java

LucidDB is the RDBMS built entirely for data warehousing and business intelligence. It is based on architectural cornerstones such as column-store, bitmap indexing, hash join/aggregation, and page-level multi versioning. Every component of LucidDB was designed with the requirements of flexible, high-performance data integration and sophisticated query processing in mind.

MongoDB - NoSQL Document Store Database

•    C++

MongoDB (from "humongous") is a scalable, high-performance, open source, dynamic-schema, document-oriented database. MongoDB bridges the gap between key-value stores (which are fast and highly scalable) and traditional RDBMS systems.

Drizzle - Database optimized for Cloud

•    C++

Drizzle is a database optimized for Cloud infrastructure and Web applications. It is designed for massive concurrency on modern multi-cpu architecture. Its memory usage is optimized for increased performance and parallelism. The Drizzle team has removed non-essential code, re-factored the remaining code into a plugin-based architecture and modernized the code base moving to C++.

sql.js - SQLite compiled to JavaScript through Emscripten

•    Javascript

sql.js is a port of SQLite to JavaScript, by compiling the SQLite C code with Emscripten. It uses a virtual database file stored in memory, and thus doesn't persist the changes made to the database. However, it allows you to import any existing sqlite file, and to export the created database as a javascript typed array. There is no C bindings or node-gyp compilation here, sql.js is a simple javascript file, that can be used like any traditional javascript library. If you are building a native application in javascript (using Electron for instance), or are working in node.js, you will likely prefer to use a native binding of SQLite to javascript.

FiloDB - Distributed. Columnar. Versioned. Streaming. SQL.

•    Scala

High-performance distributed analytical database + Spark SQL queries + built for streaming. Columnar, versioned layers of data wrapped in a yummy high-performance analytical database engine.

db2db database client

•    Java

db2db is a database client for transferring database objects (tables, their data, primary keys, foreign keys, indexes) among heterogeneous RDBMS. db2db is written in java and uses jdbc.

DbLite

DbLite is a port of a very light weight relational database management system from Java to J#. It has a SQL-like syntax and uses serialization to manage tables. It is not meant to compete with real-world relational database management systems, rather provide simple, stand-alon...

Yet Another CD DataBase-audio CD catalog

Yet Another CD DataBase Catalogs Audio CD's with automatic cdddb (and freedb) lookup. Doesn't require you to install a full RDBMS like other projects and allows you to carry your database/catalog with you a Sharp Zaurus (or a Pocket PC)

FlameRobin - Database Administration Tool for Firebird

•    C++

FlameRobin is lightweight cross platform database administration tool for Firebird RDBMS.

MyRocks - Facebook's branch of the Oracle MySQL v5.6 database

•    C

MyRocks is a Facebook's branch of the Oracle MySQL v5.6 database. It has 2x better compression compared to compressed InnoDB, 3-4x better compression compared to uncompressed InnoDB, meaning you use less space.MyRocks has a 10x less write amplification compared to InnoDB, giving you better endurance of flash storage and improving overall throughput.

CherryMusic - A music streaming server written in python

•    Python

CherryMusic is a music streaming server written in python. It helps to stream your own music collection to all your device. It provides support to share playlists with your friends. It has a built-in database, that will index your music. Find your favorite song in an instant. It plays the music inside your PC, smartphone, tablet, toaster or whatever device has a HTML5 compliant browser installed.