Is the solution above is corrcr, if yes, could you explain why? Thank you Please

Question

Is the solution above is corrcr, if yes, could you explain why?

Thank you

Please don't use handwriting in answers, because I cannot understand it.

Pubs Database Schema author(author id, first-name, last name author pub author id, pub id, author-position) book(book.id, book-title, mon year, editor) th, 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 e editor in book is a foreign key referencing author(author-id) Primary keys are underlined Pubs Database State r (author pub) (author) author id first name last name author id pub id author-position John McCarthy 2 Dennis Ritchie 2 2 D1 2 Ken Thompson Claude D1 Shannon Alan Turing G Alonzo Church 6 6 Perry White Moshe Vardi Roy Batty

Explanation / Answer

answer 1: NO, it is not correct the above relational algebra will return 7 tuples

  

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because it is a PROJECT operation in which according to the expression it will select book_title from the table book and removes any duplicate tuples so the result of the PROJECT operation is a set of tuples and hence a valid relation

answer 6 yes it is correct the above-given expression will return 11 tuples

because it is a left join on the author so it will include all the tuples from the table author and join it with where author_id=editor from table book where editor 8 and 9 are repeating so it will have total 11 tuples (9 tuples from author + 2 extra repeating tuple from book)

book_title CACM BST LMS Mind AMS AAAI

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