Which of the following is NOT a feature of relational databases?

In a relational database, data is organized into structured formats using tables, where each table consists of rows and columns. This structured approach enables the establishment of relationships between different tables through keys, supporting various operations like querying and data manipulation. Data normalization is a critical feature in relational databases as it enhances data integrity by eliminating redundancy and ensuring each piece of data resides in its most appropriate location.

When it comes to the characteristics of data within a relational database, it is fundamentally designed to handle structured data. This means that all entries in the database conform to a predefined schema, which dictates the types of data that can be stored and how they relate to each other. The presence of unstructured data, which lacks a defined format or organization—such as text documents, multimedia files, etc.—is not a feature of relational databases. Thus, the ability to manage unstructured data is not aligned with the primary design and functionality of relational databases.