Types of databases

There are two main types of databases: SQL and NoSQL. They are traditionally known as relational and non-relational databases, respectively. They differ in how they are built, the types of information they store, and how they store that information.

Relational databases

A relational database enables related data to be stored across multiple tables and is linked by establishing a relationship between the tables. A relational database management system (RDBMS) is a database management system (DBMS) that is based on this relational model.

All RDBMSs must satisfy ACID properties (atomicity, consistency, isolation, and durability). This requirement provides an efficient way to store data because it enables you to enter data once, and then reference it from elsewhere in the database.

The relationships between data sets are classified as follows:

• One-to-one: One table record relates to one record in another table.
• One-to-many: One table record relates to many records in another table.
• Many-to-one: More than one table record relates to one table record in another table.
• Many-to-many: More than one table record relates to more than one record in another table.

Non-relational databases

The term NoSQL refers to databases that do not follow traditional RDBMS principles. NoSQL is an open source database technology designed to handle big data. It was developed by Amazon, Google, LinkedIn, Twitter, and similar companies as they looked for ways to handle unprecedented data volumes and operation volumes under tight latency constraints.

NoSQL databases are designed to overcome the limitations of transactional databases. They can handle structured data, semi-structured data, and unstructured data. Unstructured data can include sensor data, information on social sharing, personal settings, photos, location-based information, online activity, usage metrics, and other data. NoSQL databases can store semi-structured and unstructured data as documents in JSON or XML format. These types of NoSQL databases are referred to as document-oriented databases. However, there are also NoSQL graph databases that store information about networks, such as professional or social connections.

NoSQL can process unstructured big data at great speed. Analyzing high-volume, real-time data such as website clickstreams can yield significant business advantages.

Next step

Properties of RDBMSs and NoSQL databases

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