Table of Contents
What is the full form of ER 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 are the three special types of entities in ER diagram and how are they represented?
Following are the main components and its symbols in ER Diagrams: Rectangles: This Entity Relationship Diagram symbol represents entity types. Ellipses : Symbol represent attributes. Diamonds: This symbol represents relationship types.
What is ER model and explain its types?
Entity Relationship Diagram, also known as ERD, ER Diagram or ER model, is a type of structural diagram for use in database design. An ERD contains different symbols and connectors that visualize two important information: The major entities within the system scope, and the inter-relationships among these entities.
What are the relationships in ER diagram?
In ER diagram, relationship type is represented by a diamond and connecting the entities with lines. A set of relationships of same type is known as relationship set.
What is ER model in DBMS?
Entity Relationship Diagram – ER Diagram in DBMS. An Entity–relationship model (ER model) describes the structure of a database with the help of a diagram, which is known as Entity Relationship Diagram (ER Diagram). An ER model is a design or blueprint of a database that can later be implemented as a database.
What are the different types of attributes in ER model?
There are five such types of attributes: Simple, Composite, Single-valued, Multi-valued, and Derived attribute.
What is the example of ER model?
Example: The roll number of a student, the id number of an employee. It is also called a key attribute. It modeled in ER diagram as a simple eclipse with underlined attribute name.
What is ER model and its features?
ER model stands for an Entity-Relationship model. It is a high-level data model. This model is used to define the data elements and relationship for a specified system. It develops a conceptual design for the database. It also develops a very simple and easy to design view of data.
What are the different types of attribute?
Types of attributes
- Single valued Attribute. Attributes having a single value for a particular item is called a single valued attribute.
- Multi-valued Attribute. Attribute having a set of values for a single entity is called a multi-valued attribute.
- Derived Attributes or stored Attributes.
- Complex Attribute.