XML Databases (eXist XML-DB, Marklogic)
An XML database is a data persistence software system that allows data to be specified and sometimes stored, in XML format.
JSON Databases (CouchDB, MongoDB, Couchbase)
JSON database is a type of nonrelational database that is designed to store and query data as JSON documents, rather than normalizing data across multiple tables, each with a unique and fixed structure, as in a relational database.
Mobile databases (Couchbase Lite, PouchDB)
A Mobile database is a database that can be connected to a mobile computing device over a mobile network
Relational Databases (Python, Oracle, MySQL)
A relational database is a digital database based on the relational model of data, used to maintain relational databases is a relational database management system.