問題一覧
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developed the ER diagram in 1976.
Peter Chen
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is a Model for identifying entities to be represented in the database and representation of how those entities are related.
Entity Relational Model
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was created to provide a simple and understandable model for representing the structure and logic of databases.
ER Model
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specifies enterprise schema that represents the overall logical structure of a database graphically.
ER Data Model
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explains the relationship among the entities present in the database.
Entity Relationship Diagram
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are used to model real-world objects like a person, a car, or a company and the relation between these real-world objects.
ER Model
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is the structural format of the database.
ER Diagram
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provides a representation of the structure of a database in a form that is independent of the physical structures required for implementation
Conceptual Data Model
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represent Entities in the ER Model.
Rectangles
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represent Attributes in the ER Model.
Ellipses
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represent Relationships among Entities.
Diamond
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represent attributes to entities and entity sets with other relationship types.
Lines
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represent Multi-Valued Attributes.
Double Ellipses
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represents a Weak Entity.
Double Rectangle
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an attribute (or combination of attributes) that uniquely identifies an occurrence of an entity.
Primary Key
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primary key composed of more than one attribute.
Composite Primary Key
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connections among two or more entities.
Relationship
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When there is only ONE entity set participating in a relation, the relationship is called a unary relationship.
Unary Relationship
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When there are TWO entities set participating in a relationship, the relationship is called a
Binary Relationship
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When there are three entity sets participating in a relationship, the relationship is called a
Ternary Relationship
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When there are n entities set participating in a relationship, the relationship is called an
N Ary Relationship