What is an ER diagram, and what is its purpose?
Name three main components of an ER diagram.
What does cardinality represent in an ER diagram?
How does an entity identifier function in an ER diagram?
What is the difference between an ER diagram and an EER diagram?
Answers and Descriptions:
Answer: An ER diagram is a visual representation of entities, attributes, and relationships in a database, used to design its conceptual schema.
Description: ER diagrams help model data requirements before implementation, ensuring clarity in database design. For example, a school database might show Students and Courses as entities with relationships.Answer: Three main components are entities, attributes, and relationships.
Description: Entities (e.g., Student) represent objects, attributes (e.g., Name, Age) describe properties, and relationships (e.g., Enrolls) connect entities. These components form the basis of ER modeling.Answer: Cardinality specifies the number of instances of one entity that can relate to another entity (e.g., one-to-one, one-to-many).
Description: For example, in a one-to-many relationship, one teacher can teach many students. Cardinality ensures accurate representation of real-world relationships in the database.Answer: An entity identifier is an attribute (or set of attributes) that uniquely identifies each instance of an entity.
Description: For example, a “StudentID” uniquely identifies each student in the Student entity. It often becomes the primary key in the logical schema.Answer: An ER diagram models basic entities, attributes, and relationships, while an EER diagram includes advanced features like inheritance and specialization.
Description: EER diagrams extend ER diagrams to support complex scenarios, such as categorizing students into undergraduates and postgraduates, enabling more detailed modeling.