Jody Fedor
IT2700: Systems Analysis & Design
Assignment #6 – Review Questions
Chapter #6 – Data Design
1. Explain the main difference between a file-oriented system and a database system.
A file-oriented system utilizes data in a regular OS file based format where a database system uses
a database engine that organizes data in a database in a table format utilizing rows for each record.
2. What is a DBMS?
Briefly describe the components of a DBMS.
DBMS stands for Database Management System. A DBMS is a collection of tools, features, and
interfaces that enables users to add, update, manage, access, and analyze the contents of a database.
A DBMS is made up of a DML (data manipulation language), Schema and subschemas, Physical
data repository, and an Interface to allow access to the database from DBA’s, Users, and Related
Information Systems.
3. Describe a primary key, candidate key, secondary key, foreign key, and common field.
Primary Key – a field or combination of fields that uniquely and minimally identifies an entity.
Candidate Key – Any field or combination of fields that can act as the primary key but are not.
Secondary Key – Any field of combination of fields that can be use to identify a entity.
Foreign Key – A field that exists in an entity that is the PK of another entity.
Common Field – An attribute (field) that appears in more than one entity (record).
4. What are entity-relationship diagrams and how are they used? What symbol is used to
represent and entity in an ERD? What symbol is used for a relationship? What is cardinality,
and what symbols do you use in the crow’s foot notation method?
An ERD graphically displays the relationship between two or more entities.
The symbol used to represent an entity is a rectangle and the relationship symbol is a diamond.
Cardinality describes the relationship between entities.
Crow’s foot notation is used to show Cardinality between entities. There are 4 symbols used, the
first is two vertical lines on the line between two entities, this represents One and only one. The second is
a “crow’s foot” and a vertical line, this represents One or many. The third is a “crow’s foot” and a circle,
this represents Zero, or one, or many. The fourth is a vertical line and a circle, this represents Zero, or
one.
5. What is data warehousing and data mining? Are the terms related?
Data Mining and Data Warehousing are related in that Data Mining is performed in a Data
Warehouse. What is a Data Warehouse, a collection of historical and or current data that may or may not
be related, collected from one or many sources. Data Mining is the activity of extracting useful
information from a Data Warehouse and determining useful relationships in seemingly unrelated data.
IT2700 – CRN 53217 – Jody Fedor – Chapter 6 – Review Questions
6. What is the criterion for a table design to be in first normal form? How do you convert an
unnormalized design to 1NF?
For a table to be in 1NF, it must not have any repeating groups. You convert an unnormalized
table to 1NF by eliminating repeating groups. You accomplish first normal form by creating a unique
record for each item in a repeating group. This creates data redundancy.
7. What are the criteria for a table design to be in second normal form? How do you convert a
1NF design to 2NF?
For a table to be in 2NF, it must first be in 1NF and all fields that are not part of the primary key
are functionally dependent on the entire primary key. You accomplish 2NF by removing all fields from a
table and placing them in another table that are not functionally dependent on the entire primary key.
You are functionally separating entities into their own tables and linking them back to the original table by
a foreign key.
8. What are the criteria for a table design to be in third normal form? How do you convert a
2NF design to 3NF?
For a table to be in 3NF, it must be in 2NF and no nonkey field can be dependent on another
nonkey field. You accomplish 3NF by removing all fields in the table that are dependent on another
nonkey field and place them in a new table that uses the nonkey field as a primary key.
9. Explain the difference between a logical record and a physical record.
The canned answer is a logical record is a set of field values that describes a single person, place,
thing, or event. Logical records as seen by an application is a group of related fields regardless of how or
where the data is stored physically. For example, across multiple hard drives or multiple tables,
databases etc.
A physical record is the smallest data unit that can be handled by the operating system and has to
do with the physical bytes that exist on a hard drive or other storage location. A physical record can
contain many logical records.
10. How would a specific date, such as May 1, 2004, be represented as an absolute date?
According to the book, on page 288, Microsoft uses Jan 1, 1900 as it's base date. If you have
excel you can use a spreadsheet to calculate the date or just use the example provided.
If May 13, 2003 is 37754, to get May 1, 2004 add 353 days and it should be 38107, but because
2004 was a leap year, it would be 38108.
If you use Excel, enter the date May 1, 2004 into a cell, then format as a number and it will also give you
38108 as the answer.
If you are writing the program, you can use any date as a base date, such as Jan 1, 2005. This
date would be 1, every additional day would add 1 to the count, at the end of the year, Dec 31, 2005, the
number would be 365 since it’s not a leap year.
Using base dates, you can calculate the distance between two dates using simple addition or
subtraction as opposed to looking up tables and doing conversions.
Some base dates are actually in seconds, this allows you to use a number to represent the entire
day and time of the event. For example, at 12:00:00 noon on Jan 2, 2005 the number would be:
Number = (Days * Hours * Minutes * Seconds) + (Hours * Minutes * Seconds) or
= (1 * 24 * 60 * 60) + ( 12 * 60 * 60)
129,600 = (86400) + (43200) = January 2, 2005 12:00:00
129,660 = January 2, 2005 12:01:00
129,720 = January 2, 2005 12:02:00
= (364 * 86400) + (43200)
31,492,800 = December 31, 2005 12:00:00
IT2700 – CRN 53217 – Jody Fedor – Chapter 6 – Review Questions