Relational databases have been the power-horse of software applications since the 80s, and continue to be so to this day. They store highly structured data with predefined columns of certain data types and requires developers to maintain their data in a structured manner. In relational databases, references to other rows and tables are indicated by referring to their (primary) key attributes via foreign-key columns. As these (joins) are computed at query time, they tend to be memory intensive and thus have an exponential cost. To overcome these constraints of a relational database, a new kind has come into the picture- graph database.
Relationships are first-class citizens of the graph data model, unlike other database management systems, which require us to infer connections between entities using special properties such as foreign keys, or out-of-band processing like map-reduce. By assembling the simple abstractions of nodes and relationships into connected structures, graph databases enable us to build sophisticated models that map closely to our problem domain. These graph data-model saw a huge traction in situations where application has to maintain complex connections between multiple nodes.
All these data-models uses client-server network architecture, where a user modifies a data and the application stores it in a centralized server. Control of the database remains with a designated authority termed as dbadmin. However, this comes with a security threat, which is, if the centralized server is compromised, the data can be altered.
Blockchain data-model consists of several decentralized nodes. Each node participates in administration: all nodes verify new additions to the blockchain, and are capable of entering new data into the database. For an addition to be made to the blockchain, the majority of nodes must reach consensus. This consensus mechanism guarantees the security of the network, making it difficult to tamper with.
Decentralized echo system eliminates the risk of a centralized control. Anyone with sufficient user access can corrupt data within a centralized system. Thus the users are reliant on the security infrastructure and knowledge of the administrator. The blockchain technology bypasses this issue by integrating the security into its core structure. However, as the writtten operations need a consensus in a blockchain technology, they tend to be time consuming for the existing blockchains in market. Though blockchain technology is well-suited to record certain kinds of information, traditional databases are better suited for other kinds of information. It is crucial for every organization to understand what it wants from a database, and gauge this against the strengths and vulnerabilities of each kind of database, before selecting one.