How to Model Relational Database Design with ERD?

The Entity-Relationship (ER) model was originally proposed by Peter Chen in 1976. An entity relationship diagram (ERD) is a graphical representation of entities and their relationships to each other, typically used for modeling the organization of data within databases or information systems.

August 24, 2015
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  1. Create a new project by selecting Project > New from the application toolbar. In the New Project window, enter Bus Route Management as the project name and click Create Blank Project.
  2. To create an ERD, select Diagram > New from the toolbar. In the New Diagram window, select Entity Relationship Diagram and click Next. Enter Bus Route Management as the diagram name and click OK.
  3. Let's start by creating the first entity, Route. Select Entity in the diagram toolbar and click on the diagram to create an entity. Name the entity Route and press Enter to confirm.
    select entity in diagram toolbar
  4. Create columns in Route. Let's start with a primary key. Right-click on entity Route and select New Column from the popup menu.
    new col
  5. Enter +id : varchar(10) and press Enter. Note that the + sign means that the column is a primary key. Varchar is the column type, and 10 is the length.
    id added
  6. Enter fare : float and press Enter, then Esc to create another column.
    fare col added
  7. Create entity Stop. A bus route has many bus stops, while a stop can be shared by many routes. Therefore, there is a many-to-many relationship between Route and Stop. Place the mouse pointer over the Route entity. Drag out the Resource Catalog icon at the top right.
    resource catalog
  8. Release the mouse button and select Many-to-Many Relationship -> Entity from the Resource Catalog.
    select many to many in resource catelog
    Name the new entity Stop. You can see that a linked entity Route_Stop is automatically created in between Route and Stop, with a foreign key added.
    stop created
  9. Create the following columns in Stop:
    Key Name Type
    PK id int(10)
      name varchar(255)
      terminus blob

    The diagram should now become:
    cols added
  10. A route has multiple bus schedules. Create an entity Schedule from Route with a one-to-many relationship. Move the mouse pointer to Route. Press and drag out the Resource Catalog icon. Select One-to-Many Relationship -> Entity to create entity Schedule.
    create one to many entity
  11. Create the following columns in Schedule:
    Key Name Type
    PK id int(10)
      departure date
      arrive date
  12. A schedule is handled by a bus. Create an entity Bus from Schedule, with a one-to-one relationship. Create the following columns in Bus:
    Key Name Type
    PK vehicle_id int(10)
      fleet_id varchar(10)
      last_main date

    The diagram should become:
    bus created
  13. A bus is driven by a bus driver. Create entity Driver from Bus with a one-to-one relationship. Add the following columns to Driver:
    Key Name Type
    PK id int(10)
      name varchar(255)
      employ_date date

    This is the final ERD.
    diagram done
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