Introduction to NoSql

In the computing system (web and business applications), there are enormous data that comes out every day from the web. A large section of these data is handled by Relational database management systems (RDBMS). The idea of relational model came with E.F.Codd’s 1970 paper "A relational model of data for large shared data banks" which made data modeling and application programming much easier. Beyond the intended benefits, the relational model is well-suited to client-server programming and today it is predominant technology for storing structured data in web and business applications.

Classical relation database follow the ACID Rules

A database transaction, must be atomic, consistent, isolated and durable. Below we have discussed these four points.

Atomic : A transaction is a logical unit of work which must be either completed with all of its data modifications, or none of them is performed.

Consistent : At the end of the transaction, all data must be left in a consistent state.

Isolated : Modifications of data performed by a transaction must be independent of another transaction. Unless this happens, the outcome of a transaction may be erroneous.

Durable : When the transaction is completed, effects of the modifications performed by the transaction must be permanent in the system.

Often these four properties of a transaction is acronymed as ACID.

Distributed Systems

A distributed system consists of multiple computers and software components that communicate through a computer network (a local network or by a wide area network). A distributed system can consist of any number of possible configurations, such as mainframes, workstations, personal computers, and so on.The computers interact with each other and share the resources of the system to achieve a common goal.

What is NoSQL ?

NoSQL is a non-relational database management systems, different from traditional relational database management systems in some significant ways. It is designed for distributed data stores where very large scale of data storing needs (for example Google or Facebook which collects terabits of data every day for their users). These type of data storing may not require fixed schema, avoid join operations and typically scale horizontally.

Why NoSQL ?

In today’s time data is becoming easier to access and capture through third parties such as Facebook, Google+ and others. Personal user information, social graphs, geo location data, user-generated content and machine logging data are just a few examples where the data has been increasing exponentially. To avail the above service properly, it is required to process huge amount of data. Which SQL databases were never designed. The evolution of NoSql databases is to handle these huge data properly.

Example :

Social-network graph :

Each record: UserID1, UserID2 
Separate records: UserID, first_name,last_name, age, gender,... 
Task: Find all friends of friends of friends of ... friends of a given user.

Wikipedia pages :

Large collection of documents
Combination of structured and unstructured data
Task: Retrieve all pages regarding athletics of Summer Olympic before 1950.

- See more at: http://www.w3resource.com/mongodb/nosql.php#sthash.lXcRhVwy.dpuf