Martika Skipworth
03/20/2007
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.

Ebay.com stores data about products that people want to auction internationally or that people just want to sell.  It also stores the consumer's as well
 as the producer's reputation in reliability in purchasing on ebay. It also store the time of availability to purchase the products and the condition of the 
product to be sold.

Blockbuster.com stores data about movies that have been released on DVD and VHS that can be taken home for entertainment.Information like availability 
and  release date. It also stores data on monthly specials that the store is having.


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.

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. 
Professor to classroom is a one to many relationship.  Professor to course is a one to many relationship.  Course to classroom is a many to many
relationship. Department to course is a one to many relationship.  

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?

It would include Album,group or artist,  year of release, type of music, and popularity.

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

A  database contains tables, where all of the information is stored in
tuples. Queries do not hold data themselves but are ways of building new tables
out of the existing tables. (Note that queries are somewhat similar to programs in that they
describe processes and actions, rather than describe information.)