1. G061 - Entity Relationship Diagrams

2. Learning Objectives: By the end of this topic you should be able to:
describe, interpret and create Entity Relationship Diagrams for a given scenario

3. Entity Relationship Diagrams
an ERD represents the structure of data in a system
relationships are the links between entities in a relational database
an ERD shows the entities & the relationships between them

4. Library Database Members of a library are loaned books Entities:
MEMBERS(MembersID, Forename, Surname, …..)
BOOKS(BookID, ISBN, Title, Author, ….)
LOANS(LoanID, MembersID, BookID, DateOut, …)

5. Library Database
MEMBERS

6. Library Database
MEMBERS
LOANS

7. Library Database
MEMBERS
LOANS

8. Library Database
MEMBERS
LOANS
BOOKS

9. Library Database
MEMBERS
LOANS
BOOKS

10. Library Database
MEMBERS
MemberID
LOANS
LoanID
BOOKS
BookID

11. Library Database
MEMBERS
MemberID
LOANS
LoanID
MemberID
BOOKS
BookID

12. Library Database MEMBERS LOANS BOOKS MemberID LoanID MemberID BookID

13. Library Database MEMBERS LOANS BOOKS MemberID Forename Surname
PostCode
LOANS
LoanID
MemberID
BookID
DateOut
BOOKS
BookID
Title
Author
ISBN

14. Library Database MEMBERS LOANS BOOKS
MemberID
Forename
Surname
PostCode
LOANS
LoanID
MemberID
BookID
DateOut
BOOKS
BookID
Title
Author
ISBN
MEMBERS(MemberID, Forename, Surname, PostCode)
BOOKS(BookID, Title, Author, ISBN)
LOANS(LoanID, MemberID, BookID, DateOut)