Table of Contents
- 1 Why do we need entity relationship diagram?
- 2 Are entity relationship diagrams used?
- 3 How do you describe an entity relationship diagram?
- 4 How can you tell if a entity is strong or weak?
- 5 What is relationship called when it is maintained between two entities?
- 6 What is the difference between ER and EER diagram?
- 7 What are the components of an entity relationship model?
- 8 What are the advantages of Entity Relationship Model?
Why do we need entity relationship diagram?
An entity-relationship diagram, or ER diagram, is essential for modeling the data stored in a database. It is the basic design upon which a database is built. ER diagrams specify what data we will store: the entities and their attributes. They also show how entities relate to other entities.
Are entity relationship diagrams used?
Database design: 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.)
What is the purpose of entity relationship diagram in software development?
Entity relationship diagrams are used in software engineering during the planning stages of the software project. They help to identify different system elements and their relationships with each other. It is often used as the basis for data flow diagrams or DFD’s as they are commonly known.
What are the benefits of entity relationship model?
Graphical representation for better understanding: An E-R model gives graphical and diagrammatically representation of various entities, its attributes and relationships between entities. This is turn helps in the clear understanding of the data structure and in minimizing redundancy and other problems.
How do you describe an entity relationship diagram?
An entity relationship diagram (ERD) shows the relationships of entity sets stored in a database. An entity in this context is an object, a component of data. An entity set is a collection of similar entities. These entities can have attributes that define its properties.
How can you tell if a entity is strong or weak?
A weak entity is dependent on a strong entity to ensure its existence….Difference between Strong and Weak Entity:
| S.NO | Strong Entity | Weak Entity |
|---|---|---|
| 1. | Strong entity always has a primary key. | While a weak entity has a partial discriminator key. |
| 3. | Strong entity is represented by a single rectangle. | Weak entity is represented by a double rectangle. |
What is entity relationship diagram?
An entity relationship diagram (ERD), also known as an entity relationship model, is a graphical representation that depicts relationships among people, objects, places, concepts or events within an information technology (IT) system.
What is the entity relationship diagram?
What is relationship called when it is maintained between two entities?
Explanation: Ellipse represents attributes, rectangle represents entity. 6. What is a relationship called when it is maintained between two entities? Explanation: Primary key of one relation used as an attribute in another relation is called foreign key.
What is the difference between ER and EER diagram?
EER diagram is an enhanced ER diagram. ER diagram is a visual representation of data based on ER model, and it describes how entities are related to each other in the database. EER diagram is a visual representation of data, based on EER model that is an extension of the original entity-relationship (ER) model.
What are the types of entity relationship?
There are three types of relationships that can exist between two entities.
- One-to-One Relationship.
- One-to-Many or Many-to-One Relationship.
- Many-to-Many Relationship.
Can a weak entity have a primary key?
Typically, a weak entity has a primary key that contains only one foreign key. The entity DEPENDENT, for example, is a weak entity because it uses the primary key of the EMPLOYEE entity as part of its own primary key.
What are the components of an entity relationship model?
The Entity Relationship Diagram (ERD) is a graphical representation of an ERM and is currently one of the most popular and widely used database design tools. The three main components of the ER Model are entities, attributes and relationships .
What are the advantages of Entity Relationship Model?
Benefits of ERD Visual representation The foremost and most important ERD benefit is that it provides a visual representation of the design. Effective communication An ERD clearly communicates the key entities in a certain database and their relationship with each other. Simple to understand ERD is easy to understand and simple to create. High flexibility
What is the relationship between entities and attributes?
In entity-relationship modeling, entities represent real world objects/things that can be identified as unique and independent, while attributes represent the properties of those entities. In relational databases, entities become tables (each row representing individual instances), whereas attributes become columns of those corresponding tables.
What is entity relational diagram?
Entity Relationship Diagram (ERD) Definition. An entity relationship diagram (ERD), also known as an entity relationship model, is a graphical representation of an information system that depicts the relationships among people, objects, places, concepts or events within that system.