Entity-Relationship (ER) diagrams define the conceptual views of databases, representing real-time entities and their relationships. They consist of elements such as entities, attributes (including simple, composite, multivalued, and derived), and various types of relationships (one-to-one, one-to-many, many-to-one, and many-to-many). ER diagrams also involve classifications like entity sets, relationship sets, and cardinality, along with concepts of generalization, specialization, and inheritance.

1. Entity Relationship Diagrams
E-R Diagrams
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2. Entity Relationship Diagrams
• ER diagrams defines the conceptual views of Database.
• Represents real time Entity and relationship among entities.
• Elements of ER Diagrams
1. Entity
Entities in a school database
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3. Entity Relationship Diagrams
2. Attributes – Properties of Entity
2.1 Simple Attributes
2.2 Composite Attributes
2.3 Multivalued Attributes 2.4 Derived Attributes
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4. Entity Relationship Diagrams
3. Relationships - Association among entities
One-to-one One-to-many
Many-to-one Many-to-many
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5. Classification of ER Diagrams
• Entity set
• An entity or group of entities with same set of attributes.
• An instance of this entity set (class) is entity type (object)
• Relationship set
• A set of similar relationship between entity types of entity set.
• Attribute Set
• An attribute or collection of attributes that uniquely identifies an entity among entity set.
• Cardinality
• the number of entities in one entity set which can be associated to the
number of entities of other set via relationship set.
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6. Cardinality Types
One-to-one relation
One-to-many relation
Many-to-one relation
Many-to-one relationwww.mbedlabs.com 6

7. • Generalization
• process of generalizing entities
• based on attributes
• Specialization
• a group of entities is divided into sub-groups
• based on attributes
• Inheritance
• the attributes of higher-level entities are inherited by the lower level entities.
Generalization
InheritanceSpecialization
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8. Example of ER Diagram
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9. Thank you
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