To have an Idea on NoSQL Databases

NoSQL databases (initially non-SQL, then Not Only SQL) are specifically designed to handle large amounts of data. They have been developed since the 1970s, but they have gained the interest of academia and industry for about two decades. This is because of their powerful characteristics and lack of relational databases, which are the most widely used data sources around the world. Indeed, these databases are based on the relational model, which is materialized by a relational database management system (RDBMS). Although RDBMS efficiently manage data (tables), they have many drawbacks that make them unsuitable for managing current data, which come mainly from Internet applications. They are called Big Data and they are used for example by Twitter, FaceBook, LinkedIn, .... They are very numerous and tend to change quickly. In fact, among the disadvantages of relational databases, we can mention: non-flexibility, non-scalability, ... On the contrary, NoSQL databases evolve very well (scaling) and almost all NoSQL databases are schema-free (we can add or delete an entity or a relationship at any time during execution). In this article, we begin by giving an overview of relational databases and their characteristics. We then describe the NoSQL databases and their main characteristics, knowing that there are as many different characteristics as  "NoSQL databases" products. We then give the taxonomy of NoSQL databases, which distinguishes four main types of NoSQL databases: key-value, wide-column, document and graphical databases. We will then give some elements of each type of database through the use of a product, an implementation of a kind of such a database