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Entity Relationship Diagrams

Entity Relationship Diagrams. Your roadmap to the database. Entity Relationship Diagrams. What is it?. Essentially, an ERD is your roadmap to the database. It details the Definition component of a database. It is a visual representation of the database components. Tables Fields Keys

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Entity Relationship Diagrams

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  1. Entity Relationship Diagrams Your roadmap to the database.

  2. Entity Relationship Diagrams What is it? • Essentially, an ERD is your roadmap to the database. • It details the Definition component of a database. • It is a visual representation of the database components. • Tables • Fields • Keys • Relationships

  3. Entity Relationship Diagrams Why? • Even the smallest databases are composed of • 5 to 10 tables • 50 to 100 fields • 15 to 30 keys • 5 to 20 relationships • ERD helps to orient the developer to the structure of an unfamiliar database. • ERD is an essential tool when working with any database.

  4. Entity Relationship Diagrams The Basics Each table is represented as a box containing a list of fields and their data types. Key fields are marked as primary key (PK) or foreign key (FK). Relationships are directional arrows originating at the foreign key and pointing to the table (parent table) containing the referenced information.

  5. Entity Relationship Diagrams Example Visual representation of both definition and data components of a table. • ERD representation • Quick • Compact • Concise

  6. Entity Relationship Diagrams Example Visual representation of both definition and data components of a table. • ERD representation • Quick • Compact • Concise

  7. Entity Relationship Diagrams Example

  8. Entity Relationship Diagrams Example

  9. Entity Relationship Diagrams Example

  10. Entity Relationship Diagrams Software • Software oriented to produce ERDs • Microsoft Visio • Microsoft Access • Dia • However, any graphical software can be utilized • Microsoft Powerpoint • Adobe Illustrator

  11. Keys and Relationships In Summary… • ERD is a roadmap to the database. • It represents the Definition of the database. • It is a developer’s strongest tool for • Familiarization with an existing database • Laying out the structure for a new database • An ERD represents definitions for • Tables • Fields • Keys • Relationships

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