Data Modeling Flashcards
what is data modeling
process of creating a layout of information fields to structure and organize data
what is data modeling used for
- means of communication with users
- blueprint for proposed database system for the organization
- used to establish a. single version of the truth
what is an external data model
-depiction of the data base system form the viewpoints of individual user groups
what does an external data model do
-provides a view of the data base from the end users point of view
-can look different for each user
`
what model resmebles the real world when seen by the end user
external data model
what is a conceptual data model
- helps in gathering business requirements and clarifying an understanding of concepts in the business
- based on info gathered from the business requirements
what form does a conceptual data model take
-usually a ERD( entity relationship diagram)
what is an ERD
-entity relationship diagram`
what is a logical data model
based on more detailed info gathered form the business requirments
which is more complex logical models or conceptual
logical
what does a logical model do
show the layout of data,
- how various entities are related to each other
- the size and type of data
what is a physical data model
-indicates the technical details for implementation as a database structure
what does a physical data model represent
-represents the actual design “blueprint” or a relational database
what is an ERD
-a chart the visually represents the relationship between database entities
what does an ERD model
- model an organizations data storeage
- 3 main components
what are the 3 main components of an ERD
- entities
- attributes
- relationships
what is an entity
noun/thing
what is a relationship
verb/what happened
what is an attribute
adjective/adverb
3 properties of entities
- represents a collection or sets
- tangible or abstract - represents sets of things that are of interest to the organization
- unique name
what is a primary key
unique identifier
-for a single instance entitty
what is a foreign key
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
what is cardinality
-the number of instances in one entity which are associated with or linked to the number of instances in another
1:1
one to one
1:M
one to many
M:M
many to many
primary key characteristics
- unique
- mandatory
- only one primary key per entity
- can be composed of many attributes
foriegn key facts
- 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
attribute facts
- 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
ERD things to consider
- 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
