Consider the below schema for a library database.

Author(authorname, citizenship, birthyear)

Book(isbn, title, authorname)

Topic(isbn, subject)

Branch(libname, city)

For each of the following Relational Algebra queries, write in English what they mean.

1. _authorname (_{birthyear>1940} (Author)) (0.25 mark)

Answer:

1. _libname (_city=Sydney (Branch)) (0.25 mark)

Answer:

_title (_{subject=alcohol OR subject=drugs} (Book Topic))