Data bases

Question 1

Data models

Answer 1

Organizes data elements and standardizes how data elements relate to one
another

Question 2

four different models and their definition

Answer 2

flat file model:
store information
in the most basic format

Hierarchical Model:
Let’s you define simple parent-child
relations and restricts access to make edits.

Network Model:
complex relations, allows for multiple access points and limited access to make edits

Relational Model:
relations between entities
with relations between integers,
strings, and other attributes.

Question 3

Traditional File Processing System

Answer 3

simple system in which the data is contained in independent tables

Question 4

File Processing Systems -
Characteristics

Answer 4

1. Separate data files are created and stored
2. Data is duplicated in separate files for separate applications

Question 5

File Processing Systems -
Problems

Answer 5

• poor security
  -limited data sharing
  -data redundancy
  -data inconsistency

Question 6

Database Approach -
Characteristics

Answer 6

a centralized collection of data organized in an efficient way that allows you to use it in many different applications. It’s stored in one location in one single database meaning you don’t have to make duplicate copies.

Question 7

Advantages of the Database
Approach

Answer 7

-improved security
-improved flexibility
-minimal data inconsistency and redundancy

Question 8

which of the different model fall under the database approach

Answer 8

hierarchical model
relational model
network model

Question 9

The relational database model…how does it work?

Answer 9

It’s a two dimensional table, in which which record has a unique identifier that link tables to one another

Question 10

primary key

Answer 10

Every table/entity has a primary key that uniquely identifies it. The number of attributes needed to uniquely identify a record is the maximum and minimum amount that it needs.

Question 11

Foreign Key

Answer 11

is the way in which the tables are being tied together, the primary key becomes a foreign key in the other table.

Question 12

True or False: All values of foreign keys must exist as values in
the parent table

Answer 12

True

Question 13

Entity Relationship Diagrams (ERD)

Answer 13

is a data model that
graphically depicts relationships between entities

Question 14

ERD - Elements

Answer 14

Entity: A person, place, object, event (example: student)

attribute: characteristics of the entity (example: student ID, student first name)

relationship: association with other entities (line between student and phone number)

cardinality: the count of instances that are allowed (on-to-one, one-to-many, many-to-many)

Question 15

Assigning Foreign Keys- ERD model

Answer 15

One to One Relationship:
take a primary key from any of the entities and put it as a foreign key in the other entity.

One to many relationship:
take the primary key in the one side and put it as a foreign key on the many side

many to many relationship: create an associative entity

Question 16

How to create an associative entity

Answer 16

Create an entity in the middle of them where there is a one to many from the parent to the associative entity. Then, place the primary keys from both entities as a combined foreign key in the associative entity.

Question 17

Data Anomalies and Normalization

Answer 17

Data anomalies include:

insertion anomaly
update anomaly
deletion anomaly

Normalization is the process in which the anomalies are being eliminated

Question 18

Writing Normalized Table Schema

Answer 18

primary keys are underlined

foreign keys are italicized

Question 19

Normalization Forms

Answer 19

First normal form:
no attributes have repeating values
,columns have distinct names, columns have consistent data types, and primary key assigned

second normal form:
full dependency on only the primary key

third normal form:
no transitive dependencies, no non-primary key attributes dependent on other non-key attributes

Question 20

Converting ER Diagrams into
Relational Tables

Answer 20

1. Each entity will convert to a table
2. Each associative entity will convert to a table
3. place the primary key and secondary keys in there respected places