Consider a database schema consisting of the following relational schemes: autho

Question

Consider a database schema consisting of the following relational schemes:

author_pub (author_id, pub_id, author_position) -Refers to author Publisher

author (author_id, last_name, first_name) – Describes Author

pub (pub_id, book_id, title) – Gives information about Publisher

book (book_id, year, editor, book_title, month) – Describes Book

- author_id in author_pub is a foreign key referencing author.

- pub_id in author_ pub is a foreign key referencing pub.

- book_id in pub is a foreign key referencing book.

- editor in book is a foreign key referencing author (author_id).

*Primary keys are underlined.

1. What question does the following expression answer?

| author_id(author) editor(book)|

2. With the help of relational algebra expression find the names of all authors who are book editors.

3. Write the relational algebra expression that return the name of all authors who are not book editors.

4. Using relational algebra expression find the name of all authors who have at least one publication in the database.

5. What question does the following relational algebra expression answer?

author (author_pub (month=’July’(book) pub))

Explanation / Answer

1. lists authors_id of authors who are not an author of any of the book in the table book

2
first_name, last_name( author_id = editor(author x book))

3
first_name, last_name( author.author_id = noneditor.author_id(author x ( noneditor ( author_id(author) editor(book)))))

4
first_name, last_name( author.author_id = pub_author.author_id (author x pub_author))

5
it contails details of author of publication, book, publisher, and publication_id of publication published in books those were published in the month of july

I hope the answer helped you :)

Related Questions

Navigate

• Browse (All)
• Browse C
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.