Question 16 Suppose a book author can be identified by an AuthorID and each book

Question

Question 16

Suppose a book author can be identified by an AuthorID and each book can be identified by an ISBN. Besides the identifier, an author and a book each has many other attributes like name, address, email, phone, and price, title, publisher, publish year, edition, etc. In general publishing business, an author may write no book or many books but every book must have at least one author.

If a data model is defined for the above business in an entity-relationship diagram (ERD) as shown below. Then, which multiplicity symbol should be used at the place pointed by the red arrow?

Question 17

If we continue on Question 16 to complete the ERD of the data model, which multiplicity symbol should be used at the place pointed by the blue arrow?

Question 18

If the data model of Question 16 and 17 is revised to replace the many-to-many relationship, a new entity, say, Contract, must be included in between Author and Book and the many-to-many relationship will be replaced by two new relationships as shown below. Then, the multiplicity at the place pointed by the red and blue arrows should be

Question 19

If the Contract entity of the ERD shown in Question 18 is implemented as a table in database, how many foreign keys it will have?

Explanation / Answer

Solution:

16)

c) is correct

Explanation:

Since the author can write no book or many book, that is why 0 or 1.

17)

b is correct

Explanation:

Since, a book is written by atleast one author but there can be many to write a book

18)

(b) at the red arrow and (d) at the blue arrow

19)

Two foreign keys.

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