NOSQL Databases.

NOSQL databases:

NoSQL databases are the one which comes in the picture when we no longer work with our traditional databases.

"NoSQL" : stand for [NOT ONLY SQL] is an replacement to traditional relational databases in big data world.
it is basically schema-free and scalable database, best suitable for solving big data challenges.

Properties of NOSQL databases.

• Schema-free: A SQL database needs to be pre-defined with schema before we can add data to it. A NOSQL database on the other hand allows data insertion dynamically. i.e. we can insert data into NOSQL database without any predefined schema.
• Scalable : Usually SQL databases scale-up vertically. i.e. when the load is high , the system will be individually upgraded. where as in NOSQL databases it is done horizontally, since these are distributed in nature.

 Types and Example of NOSQL databases:

Key-Value Stores:                ex: Redis and Amazon S3
Column-Value Stores:          ex: Hbase and Cassandra.
Document Databases:          ex: CouchBase and MongoDB.
Graph Databases:                 ex: Neo4j and MeshBase.