PostgreSQL releases its two versions 9.5 and 9.6, this year. They launched the UPSERT functionality after a long time that we know from MySQL (aka ON DUPLICATE KEY UPDATE), better full text search and speed improvements thanks to parallel queries, more efficient aggregation, replication, sorting and indexing. Postgres is used for huge, terabyte scale datasets, as well as for busy web apps, and these optimizations are welcome.
MySQL 8.0 will bring its next major release of the database. It is expected sometime in 2017 itself and it will come with a lot of improvements to the system. MySQL is still the most popular database management system and the entire industry get benefitted from these new releases.
MongoDB was initially released in 2009 and is an Open source DBMS. It is also the most popular NoSQL DB that retains some SQL properties like query and index. It supports a wide range of programming languages like Scala, Groovy, Clojure and Java It is specialized in High performance on large databases. It is best for dynamic queries and for defining indexes. It supports almost all Oss such as Linux, OSX and Windows, but on 32bit systems, the DB size is limited to 2.5 GB.
For NoSQL fans, we can recommend CouchDB. It is a fast and scalable JSON storage system which exposes a REST-ful HTTP API. The CouchDB database is easy to use and offers great performance. PouchDB is a spiritual counterpart to CouchDB that works entirely in the browser and can sync with Couch. This provides you to use Pouch in an offline ready web app, and get automatic syncing once internet connectivity is available.
Also Read: Frontend frameworks to learn in 2017
Cassandra saw its initial release in 2008 and is an Open source DBMS. It has a user-friendly interface and is useful for storing particularly huge datasets. It is Popular in banking, finance and logging, but also used by Facebook and Twitter. It has Support for Windows, Linux and OSX, as well as numerous other languages. When used with Hadoop, its Mapping/reducing is also possible.
Redis is our favorite key value store. It is small, fast and versatile. You can use it as a smart memcache alternative, as a NoSQL data store or a process messaging and synchronization channel. It offers a large number of data structures to choose from, and the upcoming 4.0 release will have a module system and improved replication.
Learn one of these: Postgres, MySQL, CouchDB, Redis.