Relational database management systems (RDBMS)

Relational database management systems (RDBMS), also known as relational databases or SQL databases, are built on the relational model that stores data against predefined schemas, and structured as interlinked tabular data. Each row in a data table typically maps to an entity or object, and the table’s columns define the entity’s fields.

These databases are highly structured and offer powerful [query languages], usually a form of [SQL], making them ideal for complex queries and transactions. Relational databases tend to be ACID compliant, making them good choices for applications that require [data integrity] to be prioritized over performance.

Relational databases can be challenging to [scale horizontally]. They tend, instead, to be scaled vertically (the capacity of individual nodes is increased as data grows). However, sharding can also be used to distribute data horizontally across multiple RDBMS instances.

By comparison, non-relational databases (aka NoSQL databases) are more flexible and scalable, but may sacrifice some of the consistency and transactional guarantees of relational databases.

Another way to classify databases is between transactional or operational databases and analytical databases.