What type of database stores data in separate entities and relates them through common fields?

• A. NoSQL Database
• B. Flat File
• C. In-Memory Database
• D. Relational Database

Answer: (D)

This question tests how data is modeled and linked across tables. In a relational database, data is stored in separate entities (tables), each representing a distinct type of data. The links between these entities are created through common fields called keys: a primary key in one table uniquely identifies a row, and a foreign key in another table references that primary key to establish a relationship. This structure lets you store related information in focused, well-defined tables and retrieve it together using joins, while keeping data consistent through referential integrity. For example, a customers table can relate to an orders table via a customer_id field. The other options describe different storage approaches: NoSQL databases model data without fixed tables and may handle relationships differently; a flat file stores all data in a single file with a simple structure; an in-memory database describes where data is kept (in memory) and can be relational or not, but the defining feature here is the relational organization through separate tables and keys.