The correct answer is option 1.
Concept:
Weak entity set :
A weak entity set is an entity set that does not contain sufficient attributes to uniquely identify its entities. In other words, a primary key does not exist for a weak entity set. However, it contains a partial key called a discriminator. Discriminators can identify a group of entities from the entity set.
ER diagram:
This ER diagram illustrates key information about the book, including entities such as author, Publisher, books, and Edition. It allows for understanding the relationships between entities.
Author:
For an author, the book dealer might want to keep track of the name (first, middle, and last), date of birth, and date of death.
Publisher:
For a Publisher, the book dealer might want to keep track of the phone, name, and address.
Book:
For a book, the book dealer might want to keep track of the id, title, and date.
Edition:
For an edition, the book dealer might want to keep track of the name and the total number of copies.
Relation ER diagram,
- The author can write a number of books and each number of books has many numbers of authors. So it has many to many relationships.
- The book can publish at most one publisher and each number of publishers has many numbers books. So it has many to one relationship.
- The book can has atmost one edition and each number edition has many numbers of books. So it has many to one relationship.
The ER diagram,
Here Edition is a weak entity because it can not have candidate key attributes.
Hence the correct answer is Edition.
Key Points
