How to create an eer diagram in smartdraw

Written by cathlene s. baptista
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How to create an eer diagram in smartdraw
Enhanced entity relationship diagrams allow engineers to logically represent data. (flow chart symbol 1 image by pixelcarpenter from Fotolia.com)

An entity relationship diagram, or an ERD, is a data model that graphically represents data, attributes and relationships in an information system. An EER diagram is a type of enhanced ER diagram that includes the concepts of superclasses, subclasses, specialisation and generalisation. Data modelers create ER and EER diagrams in order to fully understand and describe data before it is developed into a physical database. SmartDraw is a visual drawing application that provides many features that help data modelers create robust ER and EER diagrams.

Skill level:
Easy

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Things you need

  • SmartDraw software

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Instructions

  1. 1

    Open SmartDraw by clicking "Start" followed by "All Programs" and "SmartDraw." Clicking on the small "Page" icon located in the top navigation bar to open the "Home" screen. Select the "Software Design" listing from the left menu panel, and then click on the "Entity Relationship Diagram" template to create a new enhanced entity relationship (EER) diagram.

  2. 2

    Add an entity to the diagram by double-clicking the "Entity - 3" icon located in the left-hand "Library" panel. Once an entity has been placed on the diagram, click on its label and change its name from "Entity" to "Employee." The diagram now contains one item about which we want to store data -- an employee.

  3. 3

    Add two attributes to the diagram by double-clicking the "Attribute" icon located in the "Library" panel. Place the attributes near the "Employee" entity.

  4. 4

    Use the "Lines" menu, which is located in the left hand "SmartPanel," to indicate that the attributes are stored with the "Employee" entity. Rename the two attributes "Empl_id" and "Name." The diagram now contains data that should be stored about an employee -- an employee ID and a name.

  5. 5

    Add a second entity to the diagram by double-clicking the "Entity - 3" icon and changing its label from "Entity" to "Manager." The diagram now contains a second item about which we want to store data -- a manager. In this ERD, a "Manager" is considered a subclass of "Employee."

  6. 6

    Place an attribute near the "Manager" entity. Use the "Lines" menu to indicate that the attribute is stored with the "Manager" entity. Rename the attribute "Bonus." The diagram now contains data that should be stored about a manager -- a bonus. Because a "Manager" is an "Employee" subclass, it inherits the data stored in an "Employee," such as the employee ID and name.

  7. 7

    Add a third entity to the diagram by double-clicking the "Entity - 3" icon and changing its label from "Entity" to "Hourly_Empl." The diagram now contains a third item about which we want to store data -- an hourly employee. In this ERD, an "Hourly_Empl" is considered a subclass of "Employee."

  8. 8

    Place an attribute near the "Hourly_Empl" entity. Use the "Lines" menu to indicate that the attribute is stored with the "Hourly_Empl" entity. Rename the attribute "Rate." The diagram now contains data that should be stored about an hourly employee -- a rate. Because an "Hourly_Empl" is an "Employee" subclass, it also inherits the data stored in an "Employee."

  9. 9

    Place a circle on the diagram by clicking on the large "Shape" icon in the top panel and then clicking on the diagram. Place the circle near the "Employee" entity, and change its label to "d," which stands for "Disjoint." The "Disjoint" symbol indicates that an "Employee" may be a "Manager" or an "Hourly_Empl," but he may not be both.

  10. 10

    Add a single line connecting the "Employee" entity and the "Disjoint" symbol. The single line -- a completeness constraint -- indicates that an "Employee" could be a "Manager" or an "Hourly_Empl," or he may be neither.

  11. 11

    Add two single lines to the diagram that connect the "Disjoint" symbol to the "Employee" entity and the "Hourly_Empl" entity, respectively. These lines complete the relationship between the "Employee" and his subclasses -- "Manager" and "Hourly_Empl."

Tips and warnings

  • Use SmartDraw's colour capabilities to make your EER diagram more visually appealing. Resizing the entities and their labels will also make the diagram easier to read.
  • There are many ways to annotate an ER/EER diagram, including Barker notation, information engineering (crow's feet) notation and Chen notation. Use the notation that is commonly used by the organisation that will use the model.
  • Entities in an EER diagram may be physical objects, events or concepts.
  • Creating a useful and complete EER diagram requires a certain amount of theoretical database knowledge and skill. An incomplete or poorly designed logical diagram can lead to an incomplete or poorly developed physical database.

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