Which diagram is used to show entities and relationships between those entities in a database?

• A. ERD
• B. Flowchart
• C. Class Diagram
• D. Use Case Diagram

Answer: (A)

The diagram used to show entities and the relationships between them in a database is the Entity-Relationship Diagram (ERD). An ERD is built to model data structure: each entity represents a thing you store information about, its attributes define the data you record, and lines between entities show how they relate (often with cardinalities like one-to-many or many-to-many). This type of diagram is exactly what you need when designing relational databases, because it maps how tables will connect through keys and how data pieces depend on one another.

Other diagrams serve different purposes: a flowchart maps steps in a process, a class diagram models objects and their relationships in object-oriented design, and a use case diagram shows how actors interact with a system.