What defines relational data in a database?

Relational data in a database is defined by how the data is structured and interrelated. Specifically, it is linked by unique keys or identifiers, which allow for the establishment of relationships between different tables within the database. This design supports complex queries and data integrity, enabling users to efficiently retrieve and manage information from multiple related sources.

In a relational database, each table typically represents a specific entity, and the relationships between these entities are established through foreign keys that reference primary keys in other tables. This structure is pivotal for maintaining data consistency and accuracy, allowing for operations such as joins, where data from different tables can be combined based on these relationships.

The other options describe characteristics of data storage that do not align with relational databases. For example, data stored in flat files lacks the structured relationships found in relational databases. Data that is not interrelated and data stored without structure do not effectively utilize the principles of relational databases, which thrive on connections and constraints to organize and manage data systematically.