What type of data structure do relational databases primarily use?

Relational databases primarily use tables as their fundamental data structure. This approach is centered around organizing data into rows and columns, where each row represents a unique record and each column represents an attribute of that record. This tabular structure allows for efficient data management and querying through Structured Query Language (SQL).

By using tables, relational databases ensure that related data can be easily linked through relationships, which are defined using primary and foreign keys. This organization promotes data integrity and facilitates operations like joining tables, which allows for complex queries across multiple datasets while maintaining relationships among them.

Other data structures such as graphs, arrays, or objects may be used in various contexts and different types of databases, but the defining characteristic of a relational database is its table-based structure. This aligns with the foundational concepts of relational database theory established by E.F. Codd, emphasizing the importance of structured data in a way that supports robust querying and data manipulation.