Three types of database systems: Centralised, Decentralised and Distributed.
Let’s try to understand them further with an example. Suppose Phil is an entrepreneur who starts a business of house furniture. He set up various showrooms in the city for selling furniture. He created a warehouse to store all the furniture there and supply it as per the requirements of the showrooms. You can map this scenario to the centralised database system. Similar to the single warehouse storing all the furniture, the central database stores all the data.
As his business expanded, he ventured out to multiple cities by setting up various showrooms. Now, Phil realised that having one warehouse will not suffice his requirements, so he set up warehouses in all the cities. He created one warehouse in each city he ventured into. All his furniture was stored there and distributed from there to the showroom in one city. Here this can be mapped to the decentralised database system. Multiple warehouses hold the merchandise, and all the showrooms fetch the furniture from these warehouses. Similarly, in a decentralised database system, all the information is not stored in one place but in multiple places or databases.
Further, as the demand increased, Phil set up one warehouse for each showroom taking into account the cost of transportation and the nature of the market. Now every showroom has its own warehouse to store and retrieve the furniture. You can map this scenario to the distributed database systems. In a distributed database system, the data is shared across the entire network.