Week 7 - Entity - Relationship Modelling Flashcards
(16 cards)
Why is the term databases used?
It suggests the ‘ base of data’ on which all applications in an organisation are built and run
What are databases typically used for?
It primarily use is to manage internal data for organisations and businesses, even though they have support for external services.
What kinds of data might a university database include?
Students,courses,marks,staff,resources and finance.
What types of data are managed in an airline’s database?
Airplanes,parts, airports, flight, customers, travel agents, reservations, staff and finance
What is meant by an entity in a database context?
An entity is a ‘thing’ for which data needs to be stored - such as students, courses, lecturers, or exams
What are relationships in a database, and why are they important?
Relationships describe how entities are connected ( e.g students register for courses). They are crucial for correctly designing databases and linking tables together
Give examples of relationships between entities in a university database
- Students sit for exams
- Lecturers teach and assess courses
- Courses belong to degree programs
What are examples of entities that represent people in different roles?
Student, lecturer, staff member etc
What are some examples of object, organisation and conceptual entities?
Objects: Cars, airplanes
Organisations: Companies, suppliers
Conceptual: Course, degree programme
What are examples of human relationships represented in a database?
Spouse, offspring, parent etc
Give examples of role-based and event-based relationships
Role-based relationship: teaching, studying, managing
Event- based: Lecturing at, concert at
What are examples of organic relationships in a database?
Belongs to, Part of, Located at.
How do we depict relationships in database design?
Relationships are depicted using diamond boxes, with links connecting to all the entities they relate to
Define ‘Multiplicities’ in terms of a relationship and how is it represented?
It is represents the minimum and maximum number of times an entity can participate in a relationship
Give an example of multiplicities in terms of a small library
- For a book, the minimum = 0, maximum = 1 (it may or may not be borrowed, and if borrowed, only once).
- For a member, the minimum = 0, maximum = 1 (they may or may not borrow a book, but only one book at a time).
