Relational databases are data sources that display information in tables (also known as relations). BI applications are able to retrieve information from these databases in order to prepare and provide that data for analysis. Examples of relational databases include SQL Server, Oracle, MySQL, PostgreSQL, and DB2.
Relational databases are reliable, easy to create and use, and support data integrity. These benefits have made them a mainstay in the BI industry. However, as big data increases in volume and becomes more unstructured, relational databases are giving way to other big data solutions like NoSQL.
NoSQL-based solutions are one of the newer and most popular approaches for storing and retrieving structured, semi-structured, and polymorphic data without the need for complex object relational mapping. The leading NoSQL database in the marketplace today is MongoDB.