are a cornerstone of design
Models
System designers develop ______ to explore ideas and improve the understanding of the database design
Models
Engineers build a _____ of car to work out any details before putting it into production.
Model
defines the logical design and structure of a database and defines how data will be stored, accessed and updated in a database management system.
Database Model
Purpose of Models
Communicate
Categorize
Describe
Specify
Investigate
Evolve
Analyze
Imitate
is a type of flowchart that illustrates how “entities” such as people, objects or concepts relate to each other within a system
Entity Relationship Diagram
is a model used for design and representation of relationships between data
Entity Relationship Model
Is an illustration of various entities in business and the relationship between them
Entity Relationship Model
definable thing–such as a person, object, concept or event–that can have data stored about it.
Entity
Think of entities as _____
nouns
Examples: a customer, student, car or product, employees, and orders
Entity
Something that describes or qualifies an entity.
Attributes
For example, for the employee entity, the ________ would be the employee number, name, job title, hire date, department number, and so on.
Attributes
Each of the attributes is either required or optional. This state is called _______
optionality
refer to the associations or connections between tables that store related data.
Relationship
What are the uses of ERD?
Database Design
Data Troubleshooting
Business Information System
Education
Research
ER Diagrams are used to model and design relational databases, in terms of logic and business rules (in a logical data model) and in terms of the specific technology to be implemented (in a physical data model.)
Database Design
ER Diagrams are used to analyze existing databases to find and resolve problems in logic or deployment
Data Trouble Shooting
The Diagrams are used to design or analyze relational databases used in business processes
Business Information Systems
Databases are today’s method of storing relational information for educational purposes and later retrieval, so ER Diagrams can be valuable in planning those data structures
Education
Since so much research has been focuses on structured data, ER diagrams can play a key role in setting up useful databases to analyze the data
Research
defines the possibility or necessity of a relationship between two entities or entity sets. It specifies whether a relationship is required (mandatory) or optional
Modality
The relationship between two entities must exist
Mandatory
The relationship between the two entities may or may not exist
Optional
