# Relation Algebra -ER diagram- my sql quiz

Anonymous

### Question Description

Hi
I have this quiz, I need an expert to solve it in 6 hours only.

you should create a database to see the result of the relation algebra query. you can use any sourse in the internet.

### Unformatted Attachment Preview

Example questions for exam revision Question: Entity-relationship diagrams. [15 marks total] a. Draw an ER diagram based upon the following description of a book database: A book has a title, author, and a publisher. Books can have more than one author. Books can come in multiple formats including hardback, paperback, audio, and ebook. Authors may write more than one book and publishers may publish many books; authors are also not bound to a single publisher. Books may exist in a series of some kind (e.g., a ‘trilogy’, ‘saga’ etc.). Authors may enter into a publishing agreement (e.g., to write X books or one book every Y months) with a publisher. Agreements tend to have exclusivity clauses (i.e., binding author(s) to a single publisher). Explain any assumptions you make in modelling. [7 marks] b. Consider the following ER diagram, which describes a set of relationships between driving instructors, their clients and the various lesson and tests that are involved in learning to drive. i. Identify possible problems for implementing this database using SQL. Explain any modifications you would make. [3 marks] ii. Draw a set of tables that would represent the database; these should fit your modified scheme. [5 marks] Question: Relational Algebra [overall 15 marks] Consider a database with the following schema: Person ( name, age, gender ) name is a candidate key Frequents ( name, pizzeria ) (name, pizzeria) is a candidate key Eats ( name, pizza ) (name, pizza) is a candidate key Serves ( pizzeria, pizza, price ) (pizzeria, pizza) is a candidate key a. Write a relational algebra expression that finds all pizzerias frequented by at least one person under the age of 18 [3 marks] b. Write a relational algebra expression that finds all pizzerias that serve at least one pizza that Jane eats for less than £6.00. [4 marks] c. Write a relational algebra expression that, for each person, finds all pizzas the person eats that are not served by any pizzeria the person frequents. Return all such person (name) / pizza pairs. [4 marks] c. Explain, in English, what the following equation does [4 marks] ...
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