Noooooo...SQL ...!!

On what Basis are you getting Recommendations from Facebook??How your data is stored Internally in Social Network Sites ?? Have you ever thought how your information is stored by facebook in database?? Do you think its SQL that facebook is using for storing your data ?? If you think so ,then you are wrong.Its NoSQL GraphDatabase called 'Cassandra' what facebook uses to store your data.I know after reading this you will get lot of questions in your mind. 'What is Graph database??  How it looks like?? How it can be useful for Facebook Recommendations?? Where else it can be used??'.Let me explain each one in detail. What is Graph database?? I think Wikipedia gives the best answer for this question.So i think i can just add a link to wikipedia for the introduction of graphDatabase. Here you go..!! How it looks like?? I thing you got a basic idea about graph database after seeing Wikipedia page.Here i am showing sample example of a small Social Network of

                       Relational databases have been around for many decades and are the database technology of choice for most traditional data-intensive storage and retrieval applications. Retrievals are usually accomplished using SQL, a declarative query language. Relational database systems are generally efficient unless the data contains many relationships requiring joins of large tables. Recently there has been much interest in data stores that do not use SQL exclusively, the so called NoSQL movement. Examples are Google’s BigTable and Facebook’s Cassandra . Lets have a look at NoSQL  vs  MySQL (common relational database system).   When to go for  NOSQL ?? In recent years, software developers have been investigating storage alternatives to relational databases. NoSQL is a blanket term for some of those new systems. Cassandra,BigTable, CouchDB, Project Voldemort, and Dynamo are all NoSQL projects, as they are all high-volume data stores that actively reject the relatio