Data Modeling

Question 1

what is data modeling

Answer 1

process of creating a layout of information fields to structure and organize data

Question 2

what is data modeling used for

Answer 2

• means of communication with users
• blueprint for proposed database system for the organization
• used to establish a. single version of the truth

Question 3

what is an external data model

Answer 3

-depiction of the data base system form the viewpoints of individual user groups

Question 4

what does an external data model do

Answer 4

-provides a view of the data base from the end users point of view
-can look different for each user
`

Question 5

what model resmebles the real world when seen by the end user

Answer 5

external data model

Question 6

what is a conceptual data model

Answer 6

• helps in gathering business requirements and clarifying an understanding of concepts in the business
• based on info gathered from the business requirements

Question 7

what form does a conceptual data model take

Answer 7

-usually a ERD( entity relationship diagram)

Question 8

what is an ERD

Answer 8

-entity relationship diagram`

Question 9

what is a logical data model

Answer 9

based on more detailed info gathered form the business requirments

Question 10

which is more complex logical models or conceptual

Answer 10

logical

Question 11

what does a logical model do

Answer 11

show the layout of data,

• how various entities are related to each other
• the size and type of data

Question 12

what is a physical data model

Answer 12

-indicates the technical details for implementation as a database structure

Question 13

what does a physical data model represent

Answer 13

-represents the actual design “blueprint” or a relational database

Question 14

what is an ERD

Answer 14

-a chart the visually represents the relationship between database entities

Question 15

what does an ERD model

Answer 15

• model an organizations data storeage

- 3 main components

Question 16

what are the 3 main components of an ERD

Answer 16

1. entities
2. attributes
3. relationships

Question 17

what is an entity

Answer 17

noun/thing

Question 18

what is a relationship

Answer 18

verb/what happened

Question 19

what is an attribute

Answer 19

adjective/adverb

Question 20

3 properties of entities

Answer 20

1. represents a collection or sets
   - tangible or abstract
2. represents sets of things that are of interest to the organization
3. unique name

Question 21

what is a primary key

Answer 21

unique identifier

-for a single instance entitty

Question 22

what is a foreign key

Answer 22

a column of group of column in a relational database table that provides a link between data in two tables

• acts as a cross reference’
• references the primary key

Question 23

what is cardinality

Answer 23

-the number of instances in one entity which are associated with or linked to the number of instances in another

Question 24

1:1

Answer 24

one to one

Question 25

1:M

Answer 25

one to many

Question 26

M:M

Answer 26

many to many

Question 27

primary key characteristics

Answer 27

• unique
• mandatory
• only one primary key per entity
• can be composed of many attributes

Question 28

foriegn key facts

Answer 28

• does not have to be unique
• does not have to be mandatroy
• do not have to contian a alue
• name does not have tp match primary key
• data type must match primary key

Question 29

attribute facts

Answer 29

• derived attributes should not be modelled
• cannot have the same name as the within the same entity
• can have the same name if they are different entities

Question 30

ERD things to consider

Answer 30

• is the model stable
• does it support all the de data we need to store
• can is be made avaible to support additional info requirements
• is a diagram an efficient solution
• is the ERD eaisly understood
• does the design fot well with the existing database structure