The database has undergone tremendous changes since its establishment in early 1960. Navigational databases such as hierarchical databases (relying on a tree model, allowing only one-to-many relationships) and network databases (a more flexible model that allows multiple relationships) are the systems originally used to store and manipulate data. Although these early systems were simple, they lacked flexibility. In the 1980s, relational databases became popular, followed by object-oriented databases in the 1990s. Recently, NoSQL databases have emerged in response to the development of the Internet and the demand for higher speed and processing of unstructured data. Nowadays, cloud database and self-driven database are opening up new areas in how to collect, store, manage and use data.