CS101 Post Lab 3.2

1. Databases surround us on the web and everyday life. Now that you have a clearer idea of what 
database systems do, find two examples of web sites that you believe are likely to use databases 
and discuss what kinds of data they might be storing, as in the example answer. Amazon.com stores 
data about products, availability, customers, customer reviews, advertisements, etc.

A) Ebay stores information about all of the items that are up for auction and any information
relevant to those items, as well as users of the website.

B) Blockbuster.com stores information about all of the movies that they have in stock.

2. Identify relationships. Suppose you are creating a database to help a university keep track of 
its course offerings. You might have the following entities in your database, since they are distinct 
items in real life that are related to each other in important ways: course, classroom, professor, 
and department. In the space below, draw an ER diagram with a box for each of these four entities 
and arrows between the boxes labeled with the relationships they denote. (Don’t worry about what 
fields each of these entities should have for now.) See the example ER diagram in your textbook 
and in Part 1 of this lab.

Department (1) ---> (*) Professor (1) ---> (*) Course (*) ---> (*) Classroom

3. Identify many-to-one relationships. For each of the relationships you diagrammed above, which 
ones are many-to-one? Which ones are many-to-many? Indicate the relationships by writing 1 or 8 at 
each end of the relationship arrows. If you are not sure about whether a relationship is one-to-many 
or many-to-many, explain why.

One deparment has many professors
One professor teaches many courses
The course to classroom relationship is many-to-many because many courses could be taught in a 
single classroom, and a single course may be taught in many classrooms (different sections).

4. Identify entities. Suppose you are creating a database to keep track of a radio station’s record 
collection. What are some of the entities your database might include? 

Genre, Artist, Record title, Song title, Year released

5. Query results and tables look very similar—like a set of tuples. How are query results and tables 
different, however?

A table stores information.  A query is used to perform more complex tasks such as gathering information
from multiple tables for viewing, or to actually update the database itself.

In-text questions

1. Which movies were released before 1980, ordered by year of release?

The Wrong Man 1956
Psycho 1960
The Bad Sleep Well  1960
High and Low 1963
Dersu Uzala  1974
Jaws  1975

2. When were each of the Psycho movies released?

1960
1998

3. Which movies have titles that start with the letter R?

Ran (Chaos)
Red

4. Which directors have last names that start with the letter S?LastName

Sayles
Soderbergh
Spielberg

5. Which movies were directed by directors who were born after 1955?

Traffic
Cinema Paradiso
The Legend of 1900
The Children of Heaven
The Color of Paradise