INFOST 410-202 Midterm Exam
1. From the following business rules draw the Crow’s Foot ERD. (5 points)
The business rules may be written as follows:

A lecturer can lecture many classes.

Each class is lectured by one lecturer.

A lecture can advise many scholars.

Each scholar is advised by one lecture.
Answer:
2. With a diagram explain the difference between mandatory and optional participation in
an entity relationship. 2 points)
Answer:
Mandatory Participation
In the mandatory participation, for every instance of entity A, there must exist an instance of entity
B and vice versa.
Optional participation
In optional participation, it is not necessary for all the instances of the entity to participate in a
relationship. It may be that the number of instances participating for a particular entity may even
be zero.
3. What is a strong relationship? Provide an example. (2 points)
Answer:
A strong or identifying relationship is when the primary key of the related entity contains the
primary key of the “parent”.
Example:
A ROOM can only exist in a BUILDING. On the other hand, a TIRE might be considered as a
strong entity because it also can exist without being attached to a CAR.
4. Describe the use of the INTERSECT operator. (1 points)
Answer:
The SQL INTERSECT clause/operator is used to combine two SELECT statements, but returns
rows only from the first SELECT statement that are identical to a row in the second SELECT
statement. This means INTERSECT returns only common rows returned by the two SELECT
statements.
5. What is a foreign key and how is it important in a relational model? Give example (3
points)
Answer:
A foreign key is an attribute that completes a relationship by identifying the parent entity.
Foreign keys provide a method for maintaining integrity in the data (called referential integrity)
and for navigating between different instances of an entity.
Importance:
he FOREIGN KEY constraint is crucial to relational database design. It lets us link the data
according to our needs. As it creates some dependencies between the columns of primary and
foreign tables, it also lets us decide what to do ON UPDATE and ON DELETE actions performed
on the rows of the primary table.
Example:
An example of a foreign key could be in a school database, STU_ID could be a primary key that
enables the school to link students with classes in another table, where STU_ID would be present
as foreign key and allows them to link the class table back with the original student table.
6. Define entity integrity. What are the two requirements to ensure entity integrity? (3 points)
Answer:
Entity integrity is one of the primary rules of effective database construction. It refers to the
process of enforcing a primary key for each table in a database, where the key must be either a row
or a combination of rows that are unique non-null values.
The two requirements to ensure entity integrity are:
1. The primary key for each row is a unique value
2. The primary key is not null
7. State and briefly describe the four basic characteristics of Big Data databases. (8 points)
Answer:
The four basic characteristics of Big Data databases are:
Volume:
These databases are capable of housing huge amounts of data as well as having powerful
processing capabilities.
Variety:
These databases collect data from more than one source, and this data can come in different forms
such as structured, semi-structured and unstructured.
Velocity:
These databases have large amounts of data from different sources, the velocity of the data means
that more data is available at once.
Veracity:
Since these databases collect and store so much data, veracity describes the quality and accuracy
of the data that is collected.
8. What do business rules require to be effective? (2 points)
Answer:
A business rule is a statement that imposes some form of constraint on a specific aspect of the
database. Business rules allow the creator to develop relationship participation rules and
constraints and to create a correct data model. They also allow the creators to understand business
processes, and the nature, role and scope of the data.
9. List 5 sources of business rules, and what is the database designer’s role regarding business
rules? (6 points)
Answer:
The five sources of business rules are
1. Company Managers,
2. Policy Makers,
3. Department Managers,
4. Written Documentation
5. Interviews With End Users.
Regarding business rules, the database designer’s role is to ensure that the business rules are
appropriate and accurate.
10. List and briefly describe 5 problems associated with file systems? (While describing focus
on “how they challenge the types of information that can be created from the data as well as
the accuracy of the information”) (5 points)
Answer:
1. Even the simplest data-retrieval tasks require extensive programming.
2. The need to write programs makes ad hoc queries impossible.
3. System administration becomes more difficult as the number of the files in the system
4. expands.
5. Lack of security and limited data sharing
6. Making changes to an existing file structure forces changes in all of the programs that
7. use the data in that file and changes often result in bugs
11. List and briefly explain any three functions performed by the DBMS that guarantee the
integrity and consistency of the data in the database. (3 points)
Answer:
The first function performed by the DBMS that helps to guarantee the integrity and consistency
of its data would be the authorization and security management. A database needs security against
unauthorized access, ensuring that only those who are supposed to have access to the database do.
A second function that helps to guarantee the integrity and consistency of data is the management
of data manipulation. This is the mechanism that allows users to retrieve, update and delete existing
data within the database.
A third and final function that helps to guarantee the integrity and consistency of data is the
backup and recovery management. If something were to go wrong with the database and the data
within it was lost or corrupted, backups of the system help to protect against this from happening.
This prevents the loss of any data.
12.
List and describe the different types of databases regarding/considering site location
and data structure. (5 points)
Answer:

A single-user database is a database that supports one user at a time,

A desktop database is a type of single-user database that runs on a personal computer.

A multiuser database is a database that supports multiple users at a time,

A workgroup database is a type of multi user database used for a specific department in
an organization.

An enterprise database is a database that supports an entire company overall.

A centralized database is a database that has a single site location, whereas a distributed
database is a database that has two or more physically independent sites. A

Cloud database is a database that is created and maintained by using cloud services.
13. Create a Crow’s Foot ERD for each of the following descriptions. (Note: The word many
merely means “more than one” in the database modeling environment.)
a. Each of the OmwandoCo. Corporation’s division(s) is composed of many
departments. Each of those departments has many workers assigned to it, but each
worker works for only one department. Each department is managed by one worker,
and each of those managers can manage only one department at a time. (2 points)
b. During some period of time, a student can take many classes. Each of the class can be
taken by many students during that period of time. (Hint: Only 2 entities) (2 points)
14. Create the ERD from the relationship diagram between DIRECTOR and PLAY shown
in figure 14. For each entity identify all the keys, and business rules (5 points)
Figure 14 The Relational Diagram
Answer:

Each director can direct many plays, but each play is directed by only one director.

The primary keys are DIR_NUM and PLAY_CODE. The probable foreign key is
DIR_NUM.
15. Identify and describe the components of the table shown in Figure 15, using correct
terminology. Use your knowledge of naming conventions to identify the table’s probable
foreign key(s). (5 points)
FIGURE 15. The Ch03_NoComp Database EMPLOYEE Table
Answer:
There are ten records shown by the employee names. One entity set, being the table labeled
EMPLOYEE. Six attributes: EMP_NUM, EMP_LNAME, EMP_INITIAL, EMP_FNAME,
DEPT_CODE, and JOB_CODE.
There are two probable foreign keys within this table, the attribute DEPT_CODE and
JOB_CODE. Both of these probably reference separate tables with information regarding the
specific job and department.
16 Based on the following business rules, draw the crow’s foot ERM with only 1:M
relationship. (5 Points)
Hint: During some time interval, a DRIVER can drive many CARs and any CAR can be
driven by many DRIVERs
Business rules:

A driver may receive many (driving) assignments.

Each (driving) assignment is made for a single driver.

A car may be driven in many (driving) assignments.

Each (driving) assignment is made for a single car.
Answer:
17. From the Crow’s Foot ERD for the Benji Company write six business rules. (3 points)
Answer:
1. Each sales rep writes many invoices.
2. Each invoice is written by one sales rep.
3. Each sales rep is assigned to one department.
4. Each department has many sales reps.
5. Each customer can generate many invoices.
6. Each invoice is generated by one customer.
Use the database shown in Figure Ch03_StoreCo to answer Problems 18-22.
FIGURE Ch03_StoreCo Database Tables
18. For each table, identify the primary key and the foreign key(s). If a table does not have a
foreign key, write None in the space provided. (3 points)
Answer:
TABLE
PRIMARY KEY
FOREIGN KEY(S)
EMPLOYEE
EMP_CODE
STORE_CODE
STORE
STORE_CODE
REGION_CODE, EMP_CODE
REGION
REGION_CODE
-
19. Do the tables exhibit entity integrity? Answer yes or no and then explain your answer.
Particularly explain in terms of unique values and "null" values. Is it unique? Can it be Null?
(3 points)
Answer:
TABLE
EMPLOYEE
ENTITY INTEGRITY
YES
EXPLATION
Each value (EMP_CODE) in the table is
unique and there are no null values.
STORE
YES
Each value (STORE_CODE) in the table is
unique and there are no null values.
REGION
YES
Each value (REGION_CODE) in the table is
unique and there are no null values.
20. Do the tables exhibit referential integrity? Answer yes or no and then explain your
answer. Write NA (Not Applicable) if the table does not have a foreign key. (3 points)
TABLE
REFERENTIAL INTEGRITY
EXPLATION
Each
EMPLOYEE
YES
value
(STORE_CODE)
in
the
EMPLOYEE tables links to an existing
(STORE_CODE) value in the STORE table.
Each value (REGION_CODE) in the
STORE
STORE
YES
table
links
to
an
existing
(REGION_CODE) value in the REGION
table. Each value (EMP_CODE) in the
STORE table links to an existing value
(EMP_CODE) in the EMPLOYEE table.
REGION
NO
Table does not have a foreign key.
21. Describe the type(s) of relationship(s) between STORE and REGION. And, create the
ERD to show the relationships. (5 points)
Answer:
1. STORE and REGION have a 1:M relationship.
2. Each REGION can contain many STOREs, but each STORE is located in only one
REGION.
ERD:
22. Describe the type(s) of relationship(s) between EMPLOYEE and STORE. And draw the
ERD to show the relationships among EMPLOYEE, STORE, and REGION. (Hint: Each
store employs many employees, one of whom manages the store.) (6 points)
Answer:
1. EMPLOYEE and STORE have a 1:M and a 1:1 relationship.
2. Each STORE has many EMPLOYEEs, but each STORE can only have one EMPLOYEE
to manage the one STORE.
23. Using the descriptions of the attributes given in the figure, convert the ERD shown in
Figure 23 into a dependency diagram that is in at least 3NF or BNCF. (2 points)
An initial dependency diagram depicting only the primary key dependencies is shown in Figure
23 below.
Figure 23 Initial dependency diagram for Problem.
In your answer you can show functional dependencies with arrows: i.e
Doc_EmpID --> (Doc_FName, Doc_LName, Doc_CellPhone) or draw using MS word tools
for shapes
24. Use the dependency diagram shown in Figure 24 to work the following problems.
Figure 24 Initial Dependency Diagram for Problem 24
A
B
C
D
E
F
G
a. Break up the dependency diagram in Figure 24 to create two new dependency diagrams,
one in 3NF and one in 2NF. (2 points)
3NF Dependency Diagram:
2NF Dependency Diagram:
b. Modify the dependency diagrams you created in Problem 24a to produce a collection of
dependency diagrams that are all in 3NF. (Hint: You will have more than two diagrams). (3
points)
Answer:
c. Modify the dependency diagrams you created in Problem 24b to produce a collection of
dependency diagrams that are all in BCNF. (4 points)
25. a. What are the applications of ERD and normalization? Give an example. (2 points)
Answer:
ERD or the entity relationship diagram is used to develop and design databases and normalization
is used in optimizing those databases. An example of the application of these would be anything
that required data to be stored into a database like a retail inventory system, a school’s student
database and much more.
b. Briefly describe the conditions that must be met for a table(s) to be in 1NF, 2NF, 3NF,
BCNF and 4NF. (5 points)
Answer:
1NF (First Normal Form) Rules


Each table cell should contain a single value.
Each record needs to be unique.
2NF (Second Normal Form) Rules


Rule 1- Be in 1NF
Rule 2- Single Column Primary Key that does not functionally dependant on any subset
of candidate key relation
3NF (Third Normal Form) Rules


Rule 1- Be in 2NF
Rule 2- Has no transitive functional dependencies
BCNF (Boyce-Codd Normal Form)
It is stricter than 3NF. A table is in BCNF if every functional dependency X → Y, X is the super
key of the table. For BCNF, the table should be in 3NF, and for every FD, LHS is super key.
4NF (Fourth Normal Form) Rules
If no database table instance contains two or more, independent and multivalued data describing
the relevant entity, then it is in 4th Normal Form.