Entity Relationship Diagram (ER – Diagram)
The entity-relationship diagram is a set of entities that describes the database through the diagram. It is also known as the ER – diagram. The ER model defines the conceptual view of a database. It works around real-world entities and the associations among them. At the view level, the ER model considered a good option for designing the database.
An entity-relationship diagram consists of an entity, attributes, and relationship. Short explanations for its components are as follows:
An entity can be a real-world object, either animate or inanimate, that can be easily identifiable. For e.g. in a school database students, teachers, classes, and courses offered can be considered as entities. May an entity is a collection of similar types of entities. An entity set may contain entities with attributes sharing similar values.
Entities presented by means of their properties called attributes. All attributes have values. For e.g. a student entity may have name, class, and age as attributes. There exists a domain or range of values that can be assigned to attributes.
Another e.g. a student’s name cannot be a numeric value. It has to be alphabetic. A student’s or people age cannot be negative, etc.
The association among entities is a relationship. For e.g. an employee works at a department, a student enrolls in a course. Here, works and enrolls called relationships.
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Solution of financial accounting PU 2018
Symbols used in Entity Relationship Diagram (ER – Diagram)
PU 2016 Spring Q. No. 17
What is an ER Diagram? Draw
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