What is a defining feature of a non-relational database?

Reporting across multiple data sources is a feature of data warehouses and BI tools, not a defining characteristic of non-relational databases specifically.

A strictly enforced schema is a defining characteristic of relational databases, which is the opposite of the flexible schema approach used by non-relational databases.

NoSQL databases use flexible data models such as document, key-value, wide-column, or graph structures that do not require a fixed schema, allowing different records to have different fields and data types. This flexibility enables developers to iterate quickly and store varied or hierarchical data without costly schema migration operations. It is the fundamental characteristic that differentiates NoSQL from relational databases.

Joining multiple tables using SQL is a core feature of relational databases and is not a characteristic of non-relational databases, which typically avoid joins in favor of denormalized document structures.