NoSQL

NoSQL databases refer to database management systems (DBMS) that differ from RDBMS in some way. NoSQL databases avoid join operations and normally scale out horizontally.

Here are some of the advantages of NoSQL datbases.

Advantages

• Elastic scaling: NoSQL databases scale out horizontally. Usually we can add low-cost commodity servers and scale NoSQL databases.
• Big data: NoSQL databases are normally designed to handle huge unstructured data. Social Networking sites such as Facebook, Linkedin use NoSQL systems for their operation.

• Less DBA requirement: NoSQL databases require less interference from database administrator. With designs such as read-repair, data distribution and replication there is less administrative task left for the DBA.
• Flexible data models: NoSQL systems such as MongoDB is document-based database. It does not have any inherent schema requirement. Thus the schema of the data can change on the fly.

However there are some challenges of NoSQL, which should be kept in mind.

Challenges

• Maturity: NoSQL databases have recently started gaining momentum. There are not many experts who know these systems in and out and most of the databases are not mature.
• Support: NoSQL databases are mostly open-source and built with the help of community effort. Therefore they may lack quick support, customer care, etc.
• Administration: NoSQL databases installation require good technical skills. The maintenance of these systems is also tedious.
• Expertise: There are few NoSQL developers and most of them are still in the learning phase.

Categorization

NoSQL implementations can be categorized by their manner of implementation.

Here are different categories along with an implementation.

• Document store : MongoDB
• Graph : Neo4j
• Key-value store : Voldemort
• Wide-column : Cassandra