ER Diagrams - CCEA - SSD (copy)

What is an Entity-Relationship (ER) model?

A high level conceptual model used in database design concepts

What are ER models used for?

to visually represent the structure of a database by identifying entities, relationships, and attributes.

What are the main components of an ER model?

Entities in the system, relationships between the entities, and attributes of entities and relationships.

What does an ER models help to do?

-Represent data requirements of a system
-Define data structures before implementation in a relational database
-Facilitate communication between stakeholders during system analysis and design

What does an entity represent in an ER model?

A set of objects or concepts (persons, places, things, or events) about which data is to be. recorded and maintained relevant to the organisation.

How is an entity represented in an ER model?

By a rectangle labelled with a singular noun.

What is a relationship in the context of ER models?

A meaningful association between two entities, labelled with verbs. E.g (1:1) or (1:M)

What is cardinality in ER models?

The maximum number of times an entity participates in a relationship, such as one-to-one, one-to-many, or many-to-many.

What is a one-to-one relationship?

A relationship where one entity is associated with one instance of another entity. E.g one country has one capital city

What is a one-to-many relationship?

A relationship where one entity is related to many instances of another entity. E.g one customer can buy many items

What is a many-to-many relationship?

A relationship where many instances of one entity relate to many instances of another entity. E.g many students can sit many exams

What is the purpose of normalisation in database design?

To validate the model and ensure that many-to-many relationships are decomposed into one-to-many relationships.

What is the role of an ER model in system design?

To represent data requirements, define data structures, and facilitate communication between stakeholders.

What is the significance of attributes in an ER model?

Attributes provide details about entities and relationships.

What type of approach do ER models use in system design?

A top-down approach to the design and implementation of a system.

Can ER models be used for different types of databases?

Yes, they can be used for relational, hierarchical, or network databases.

Does an ER model depend on a certain programming language?

NO it can be used regardless of database or programming language

What does an analyst do with an ER model?

They modify it to fit the specific data model being used e.g relational, hierarchical

What is developed when using the relational model?

A scheme outlining the tables that will be used in the system

What receives particular focus when identifying fields within tables and why?

Primary and foreign keys, to help ensure that any many to many relationships have be decomposed to one to many

What technique can be used to validate the relational modal?

Normaliseation

What is the final step after completing the relational model?

Selecting the most appropriate DBMS (e.g MySQL or Access)

How are attributes represented in an ER diagram

With an ellipse

How are relationships represented in an ER diagram

With a diamond

How are attributes to entities and entitie sets with other relationship types represented in an ER diagram

With a line

How are multi-valued attributes represented in an ER diagram

With a double ellipse

How is a weak entity represented in an ER diagram?

With a double rectangle