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Conceptual Database Model. Entity Relationship Diagram (ERD).
Contents
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Conceptual, logical and physical data models
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What is an ER diagram?
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History of ER models
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Uses of entity relationship diagrams
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Mapping natural language
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The components and features of an ER diagram
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Entity Relationship Diagram Tutorial
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Create ERD from existing database.
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Different Types of Keys in DBMS
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ERD symbols on several notation styles
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ERD Examples
Learn the essentials of ER Diagrams and ER Models, along with their origins, uses, examples, components, limitations and guidelines on
how to draw them using our ER diagram tool.
Conceptual, logical and physical data models
ER models and data models are typically drawn at up to three levels of detail:
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Conceptual data model: The highest-level view containing the least detail. Its value is showing overall scope of the model and
portraying the system architecture. For a system of smaller scope, it may not be necessary to draw. Instead, start with the logical
model.
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Logical data model: Contains more detail than a conceptual model. More detailed operational and transactional entities are now
defined. The logical model is independent of the technology in which it will be implemented.
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Physical data model: One or more physical model may be developed from each logical model. The physical models must show
enough technology detail to produce and implement the actual database.
Sometimes, engineers will branch out ER diagrams with additional hierarchies to add necessary information levels for database design. For
example, they may add groupings by extend up with superclasses and down with subclasses. It is Extended ERD.
© Yuriy Shamshin
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