1.Entities:
Entities represent real-world objects or concepts, such as customers, products, employees, etc. Each entity is typically depicted as a rectangle in the diagram. Entities have attributes that describe the properties or characteristics of the entity.
2.Attributes:
Attributes are the properties or characteristics of entities. They provide more detailed information about the entities they belong to. Attributes are often listed within the rectangles representing entities in an ERD.
3.Relationships:
3.Relationships:
Relationships describe how entities are related to each other within the database. They illustrate the connections or associations between entities. Relationships are depicted as lines connecting entities, and they may have cardinality and participation constraints.
4.Primary Key:
4.Primary Key:
A primary key is a unique identifier for each entity within a database table. It ensures that each record in the table can be uniquely identified. In an ERD, primary keys are typically underlined within entity rectangles.
5.Foreign Key:
5.Foreign Key:
A foreign key is a field in a database table that refers to the primary key of another table. It establishes a link between two tables, allowing for the creation of relationships between them. Foreign keys are represented in ERDs to indicate relationships between entities.
6.Cardinality:
6.Cardinality:
Cardinality specifies the number of instances of one entity that can be associated with the number of instances of another entity in a relationship. It defines the minimum and maximum number of occurrences allowed in a relationship, such as one-to-one, one-to-many, or many-to-many.
7.Participation Constraints:
7.Participation Constraints:
Participation constraints indicate whether each entity in a relationship must participate in the relationship. They specify the minimum and maximum participation of entities in a relationship, such as mandatory participation (total participation) or optional participation (partial participation).
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