1 / 11

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

azana
Télécharger la présentation

Entity Relationship Diagrams

An Image/Link below is provided (as is) to download presentation Download Policy: Content on the Website is provided to you AS IS for your information and personal use and may not be sold / licensed / shared on other websites without getting consent from its author. Content is provided to you AS IS for your information and personal use only. Download presentation by click this link. While downloading, if for some reason you are not able to download a presentation, the publisher may have deleted the file from their server. During download, if you can't get a presentation, the file might be deleted by the publisher.

E N D

Presentation Transcript

  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

More Related