Question

Given the following relation, what are potential Multivalued Dependencies (MVDs)? title, author, number_pages, publisher) author-(name, age) publisher (name, city)

Answer 1

For a given book, number_pages can not be changed, but can have multiple authors and publishers.

since, authors and publishers are independent from each other, but both are dependent on title.

{title} ->> {author}

{title} ->> {publisher}

so, column author and publisher are multivalued dependent on column title.

example: Book (title, author, number_pages, publisher)

title	author	number_pages	publisher
B001	A001	100	P001
B001	A002	100	P002
B002	A001	150	P001
B003	A002	200	P003
B003	A003	200	P004

author( name, age)

name	age
A001	28
A002	30
A003	28

publisher( name, coty)

name	city
P001	C001
P002	C001
P003	C002
P004	C003

In book table, we can see that B001 has multiple authors A001 and A002 and number of pages of book B001 is 100 (because both authors are writing same book), but publishers of B001 is P001 and P002. Since, there are more than one independent maltivalued attributes which depends on attribute title. so, {title}->>{author} and {title}->>{publisher} are multivalued dependencies.