A non-relational, or NoSQL database, is a database that does not organize its data based on relations. Unlike relational databases, there are different ways in which the different non-relational databases store and manage their data. Some store data as key-value pairs, while others store data as objects. A number of these database options support Android. In most cases, these databases come with the ability to synchronize your data to an online server. Two of the most popular No-SQL mobile databases are:

• CouchBase Mobile
• Realm

CouchBase is an example of a document database and Realm is an example of an object database.

Document databases are schema-less, which means they are unstructured and as such do not have restrictions on what can go into a document. They store their data as key-value pairs.

Object databases, on the other hand, store their data as objects.