Draw an ER diagram that encodes the following business rules. Clearly mark all key and participation constraints.

Transcription

1 CS 500, Fundamentals of Databases Midterm Exam Completed between February 16 th (9am) and February 18 th (11pm), 2018 SOLUTIONS Problem 1 (20 points): ER modeling Draw an ER diagram that encodes the following business rules. Clearly mark all key and participation constraints. Diseases are identified by a, and are further described by the primary structure they affect and by a prognosis. Viruses are identified by a genus and a species. Some diseases are caused by viruses. Only viruses that cause some disease are recorded in our database. Symptoms are identified by a, and are further described by severity and duration. Each symptom is associated with at least one disease, and each disease has one or several symptoms. Patients are identified by a social security number (SSN), and also have a and an age. Each patient is being treated for exactly one disease by exactly one doctor. Doctors are identified by a social security number (SSN), and also have a and an age. A doctor can treat any number of patients and is qualified to treat any disease. 1

2 Problem 2 (30 points): ER to relational translation Consider ER diagrams below. Write one or several create table statements that implement the entity sets, relationship sets and constraints encoded by the diagrams. You may assume that all attributes are of type integer or are variable-length strings of length up to 64. Give a brief explanation of your implementation, explaining how you encoded the constraints specified by the diagram. If a constraint cannot be encoded you must state so explicitly. Satellites diameter mass orbital_period Planets orbit period orbit d after brightness mythology Stars metallicity Deities create table Deities ( varchar(64), mythology varchar(64), primary key (, mythology)); create table Stars ( varchar(64) primary key, brightness integer, metallicity integer); create table Planets ( varchar(64) primary key, diameter integer, mass integer, star varchar(64) not null, period integer, deity varchar(64), mythology varchar(64), foreign key (star) references Stars(), foreign key (deity, mythology) references Deities (, mythology)); 2

3 create table Satellites ( varchar(64), planet varchar(64), orbital_period integer, primary key (, planet), foreign key (planet) references Planets() on delete cascade ); All constraints are encoded. Problem 3 (40 points): Relational algebra and SQL Consider three relations that store information about Films and Awards, along with instances that illustrates these schemas. Write queries that compute the required information in the specified language. There is no need to show query results, instances are given for illustration only. The database creation script is available at 3

4 (a) (5 points) (SQL) List all awards received by films for which the revenue exceeds the budget by at least a factor of 10. Result should have the schema (film, award, category, year). select A.film, A.award, A.category, A.year from Awards A, Films F where F.film = A.film and F.revenue >= F.budget * 10; (b) (5 points) (SQL) For each studio and genre, compute the number of films of that genre produced by the studio, and the total profit that the studio made on those films. Only include genres for which the studio produced 2 or more films. Result should have the schema (studio, genre, num_films, total_profit). select studio, genre, count(*) as num_films, sum(revenue - budget) as total_profit group by studio, genre having count(*) >=2; (c) (10 points) (Relational algebra) List s of studios that either (a) produced films with a revenue of 1,000 or higher that did not win any awards; or (b) did not produce any animation films. List each studio exactly once. Result should have the schema (studio). (π studio (π studio, film (σ rev 1000 F) π studio, film ( A A. film=f. film F))) (π studio (F) π studio (σ genre=animation (F))) (d) (10 points) (SQL) List s of studios that either (a) produced films with a revenue of 1,000 of higher that did not win any awards; or (b) did not produce any animation films. List each studio exactly once. Result should have the schema (studio). select studio from ( (select studio, film where revenue >=1000 EXCEPT select F.studio, F.film F, Awards A where F.film = A.film) ) UNION (select studio EXCEPT select studio where genre = 'animation'); 4

5 (e) (10 points) (Relational algebra) List pairs of films produced by the same studio such that one of the films received an Oscar and the other did not. List each pair exactly once. Result should have the schema (film1, film2). π F1. film,f 2. film ( ρ F1 (π A. film,f.studio (σ award='oscar ' ( A) A. film=f. film F)) F1.studio=F 2.studio ρ F 2 (π film,studio (F) π A. film,f.studio (σ award='oscar ' ( A) A. film=f. film F))) 5