Databases exercises
Dr. Paolo Coletti – Free University of Bolzano Bozen
08 February 2016
Databases
Draw the schema of this database, using at least (more if necessary): 3 tables, a junction table, 15 fields in the entire
database. Try to make the database as complete as possible, keeping it simple and not contorted. You must indicate
very clearly field names, MySQL field types, primary keys and other options, at least two constraints, relations with
their “1” and “many” sides and the fields involved in the relations. For all the fields whose name is not obvious, you
must also include a small comment that lets everybody understand what the field should contain. You must also
justify non-standard choices.
Moreover, suggest two new queries (in English not in SQL): one which involves at least two tables and another one
which needs a summary query to be implemented.
Travel Agency
A travel agency needs a database to keep track of all the available hotel/resorts and of the customers. For each
customer the database must include the personal information, the destinations (which hotel) and the dates of
departure and arrivals of his trips. The travel agency is also interested in keeping record of which employee was
involved in reserving a specific trip for a given customer. The database must be able to answer the question: “What is
the average number of stars of mountain resorts visited by customer John Smith?”
Research Institute
This temporal database is designed to keep record of all the research projects conducted by a research institute with
the involved researchers. Each researcher belongs to a research unit, which has a specific goal and a location in the
buildings, and is involved in several project for a different amount of months. Each project is characterized by a
research area, duration, funding. The database should be able to answer the question “How many researchers of the
Theoretical Physics unit have been involved in projects funded by the European Union?”
Airline company
This static database handles information about flights and airplanes of an airline company. The goal is to keep track of
the specific airplane used in a specific flight (a flight has a day of the week, times, destination, arrival and it is repeated
in the same way with the same airplane every week). Each airplane is identified by a code and has a purchase date, a
model and manufacturer. The company owns several airplanes of different models and for each model the technical
details (number of seat, maximum flight length, maximum speed) has to be stored. The database should be able to
answer the question "What is the average number of seats of airplanes which depart from Rome?".
Medical clinic
This temporal database handles information about customers of a private medical clinic. Each client is identified by an
ID, name, surname, birth date, address and phone number. For each client the clinic managers want to keep track of
the specialist visits with time, date and personal details of the involved doctor (we assume that for each visit there is
only one doctor). Each visit is identified by a code and has a description, a cost and is offered by a specific unit of the
clinic (i.e. cardiology, surgery, etc.). The database should be able for each client to retrieve doctor, time, date and type
of each visit..
Recruitment company
This database handles the data of a recruitment company. For each worker, all his working periods should be recorded
and each one with all the acquired skills he/she has learnt in that period and their level of expertise. The database
Databases exercises
Paolo Coletti
must be able to create a report of the career of each worker and to retrieve all the workers whose profile satisfy a
given list of skills and expertise.
Politicians
this temporal database handles information on politicians, parties and governments they have been involved in. Each
politician has belonged to different parties during his career and may have had government roles for given periods of
time. The database must be able to produce a report with the political career of a given politician.
Recipes
this static database handles data on recipes and ingredients. Each recipe has a short and long description, time,
difficulty, cost and many ingredients in different quantities. Ingredient unfortunately use several units of measure
(litre, Kg, gram, ...). The database must be able to produce a report with the recipe’s description and the list of
ingredients with their quantities.
Bookshop’s inventory
this static database handles data on books, editions with their ISBN, editors and authors. Each book is printed in
several editions by different editors with different features and the bookshop has some copies in its storehouse. The
database should be able to answer to the question “how many copies of Romeo and Juliet’s editions of less than 100
pages do we have?”.
Zoo
this static database handles data on each single animal, keeper and cage. There is more than one animal per cage and
keepers make 8-hours turns for groups of cages. The database should be able to answer to the question “who are the
responsible ones for the horses during the night?”.
Animal shop
this temporal database handles data on each single animal, its daily food and the buyer. Each animal eats more than
one type of food and can have only one buyer. The database should be able to answer to the question “how much
corn per day do animals currently present in shop eat?”.
Students association
this temporal database handles data on each member, its degree, the association’s roles and all the fee payments.
Each member may have only one role but in time s/he may have had different roles, each member is enrolled or was
enrolled to only one degree course. The yearly fee is the same for all students, but varies from year to year and we
want to know exactly who has paid what and when. The database should be able to answer to the question “how
many president we had enrolled to EM between 2004 and 2009?”.
Olympic games
this static database handles data on each team and participant, each competition and the results. Clearly each athlete
belongs only to one team but can participate to different games. Some games have a team participation instead of
single athletes participation. The database should be able to answer to the question “how many silver medals has
Finland won?”.
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Databases exercises
Paolo Coletti
Proposed solutions
Warning: these are databases as I would build them. Any other implementation which is correct and satisfies the
requites is fully accepted. There might be cases where requirements are so open that a completely different schema
and idea is correct.
Warning: reading these solutions before doing the database is a wonderful way to spoil yourself of the possibility to
do exercises. These are meant to be exercises and not examples: I remind that you learn much more by trying to do
them and then checking rather than by looking at solution.
Travel Agency
Resorts:
 ID: integer, auto_increment, primary key
 Phone, email: varchar(30)
 ContactPerson: varchar(50)
 ResortName, Town, Country: varchar(50), not null, index
 Address: varchar(100)
 ZIP: varchar(10)
 Type: ENUM(“mountain”, “seaside”, “country”, “lakeside”, “island”), index
 Stars: integer, not null, index
 Constraint: Stars between 1 and 5
Bookings:
 ID: integer, auto_increment, primary key
 Customer, Resort, Madeby: foreign keys, same type as corresponding primary key, index
 From: Date, index, not null
 To: Date, index
 DateMade: datetime, not null, index, default {CURDATE()}
 NumberPeople: integer, not null, default {2}
 FoodIncluded, TravelIncluded: ENUN(“yes”,”no”), not null, default{“no”}
 Constraint: NumberPeople between 1 and 999;
 Constraints: DateMade <= CURDATE()
Customers:
 ID: integer, auto_increment, primary key
 LastName: varchar(30), not null, index
 PlaceBirth, FirstName, Phone: varchar(30)
 DateBirth: Date
 Phone: varchar(30)
 Address: varchar(100)
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Databases exercises
Paolo Coletti
 Constraints: DateBirth < CURDATE()
Employees:
 TaxCode: char(16), primary key
 LastName: varchar(30), not null, index
 PlaceBirth, FirstName: varchar(30), not null
 DateBirth: Date
 Nationality: varchar(30), not null, index
 Sex: ENUM(“M”,”F”), not null, index
 Address: varchar(100)
Primary keys are always unique, not null, index.
Star is number, as no 0 stars or unrated resorts are possible.
ZIP can be null because some very small countries may not use it.
Query using more than one table: in which resort will John Smith be on the 27th May 2011?
Summary query: how many people has our travel agency in hotel Villa Bianca on the 27th May 2011?
Research Institute
Researchers:
 TaxCode: char(16), primary key
 LastName: varchar(30), not null, index
 PlaceBirth, FirstName: varchar(30), not null
 DateBirth: Date
 Nationality: varchar(30), not null, index
 Sex: ENUM(“M”,”F”), not null, index
 Unit: foreign key, same type as corresponding primary key, index
Units:
 ID: integer, auto_increment, primary key
 UnitName: varchar(60), not null, index
 Floor: varchar(10)
Projects:
 ID: integer, auto_increment, primary key
 ProjectName, ResearchArea: varchar(100), not null, index
 StartDate: Date, not null, index
 EndDate: Date, index
 Totalfunding: decimal(11,2)
 FundingOrganiz: varchar(100), index
 Constraint: Totalfunding IS NULL or TotalFunding>=0
 Constraint: EndDate IS NULL or EndDate>StartDate
Participations:
 ID: integer, auto_increment, primary key
 Researcher, Projects: foreign keys, same type as corresponding primary key, index
 Start: Date, not null, index
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Databases exercises
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Paolo Coletti
End: Date, index
ParticipationPercentage: decimal(4,3), not null
Role: varchar(50), index
Constraint: ParticipationPercentage between 0 and 1
Constraint: End IS NULL or End>Start
Primary keys are always unique, not null, index.
End fields are not required since projects and participation may be without end. Total Funding is not required since it
may be “to be determined”. Role is not required since the participant may be without role. ParticipationPercentage is
indicated in decimal form (0,750 for 75%) and not with percentage symbol.
According to this database only a single funding organizations is possible for each project. Moreover, several Units
may exist with the same name but different locations (since UnitName does not have “unique” option).
Query involving more than one table: what are the projects in which John Smith is participating?
Summary query: what is the total funding for projects to which John Smith is currently participating?
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