Dears,,

I want answers to this question:

Q1:

author(author_id, first_name, last_name)

author_pub(author_id, pub_id, author_position)

book(book_id, book_title, month, year, editor)

pub(pub_id, title, book_id)

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- How many tuples will be returned by the following relational algebra query?

_{book_title}(book)

2- What question does the following expression answer?

_{author_id} (author) _editor(book)

3- Write a relational algebra expression that returns the names of all authors who are book editors.

4- How many tuples are returned by the following relational algebra expression?

author _{author_id=editor} book