Draw Entity Relationship Diagram (ERD)
Entity relationship diagram (ERD) is a kind of diagram for presenting visually the structure of relational database. In this tutorial we will make use of ERD to model the database structure of a simple bus route management system.
| May 19, 2010 | |
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- Start VP-UML. Select a new workspace folder for this tutorial.
- Select File > New Project to create a project. Name the project as Bus Route Management and confirm.
- Create an Entity Relationship Diagram. Right click on Entity Relationship Diagram in Diagram Navigator and select New Diagram from the popup menu.
- This creates an ERD. Name the diagram Bus Route Management at the top left corner of the diagram, and press Enter.
- Let's start by creating the first entity Route. Select Entity in diagram toolbar and click on the diagram to create an entity. Name the entity Route and press Enter to confirm.
- Create columns in Route. Let's start with a primary key. Right click on entity Route and select New Column from popup menu.
- 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.
- Enter fare : float and press Enter, then Esc to create another column.
- Create entity Stop. A bus route have many bus stops, while a stop can be shared by many routes. Therefore, there is an many-to-many relationship between Route and Stop. Move the mouse pointer over Route and press on the resource icon Many-to-Many Relationship.
- Drag it out and release the mouse button. Name the new entity Stop, You can see that a linked entity Route_Stop is automatically created in between Route and Stop, with foreign key added.
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Create the following columns in Stop:
Key Name Type PK id int(10) name varchar(255) terminus blob
The diagram should now become:
- A route have multiple bus schedules. Create an entity Schedule from Route with a one-to-many relationship. Move the mouse pointer to Route, Make use of the resource icon One-to-Many Relationship to create entity Schedule.
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Create the following columns in Schedule:
Key Name Type PK id int(10) departure date arrive date -
A schedule is handled by a bus. Create an entity Bus from Schedule, with an 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:
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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.
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Comments (17)
written by richard on July 15, 2010
Good easy to follow example for someone like me just starting/learning.
It appears the instructions above for 14 creating the entity Bus are incorrect
(should be- vehicle_id not id).
Also 15 (should be- Finally, create entity Driver from Bus, with an one-to-one relationship. Create the following columns in Driver.)
written by Bartek on August 6, 2010
Looks wrong
15. A bus is driven by a bus driver. Finally, create entity from Bus with a one-to-one relationship.
Create an entity Bus from Schedule, with an one-to-one relationship. Create the following
columns in Bus:
written by Michael on August 24, 2010
Using this sample, can you tell me how I would show which tables contribute to a view. I've created a view entity but I'd like to show which tables make up the view visually but don't see a way to do that. Thanks in advance.
written by ghattamaneni on December 4, 2010
this is very easy to understand who is initially learners for E-R diaghrams
written by Jick Yeung on January 10, 2011
Hi Richard and Bartek,
Thank you for pointing out the mistakes. All issues are now fixed.
Best regards,
Jick Yeung
written by Thileep vec on February 1, 2011
excellent tutorial for basic learners of E-R diagram in visual paradigm
written by Ashique on February 9, 2011
The way of explanation is good,
and easy to follow for a beginner like me.
regards,
ash
written by Graham on March 2, 2011
Excellent tool for generating ERDs, I'm sure my students will make great use of this tool.
written by caci on March 12, 2011
In the entity diagram J have a primary key, and J wanna to have a secundary key in a new column, how to do that?
Sorry about my english.
written by caci on March 12, 2011
hhhh in the relationship specification we can mark the colum from some entity with the foreign key (at school we caled it secundary key, it is more logicaly :) and at the screen he apear with the green arrow !
Thanks anyway!
written by JouBSTi on July 26, 2011
Is it also possible to show user types in the diagram?
I can't find any setting to realize that.
written by Jick Yeung on July 26, 2011
Dear JouBSTi,
You can show the user type defined in column specification window. Please try this:
1. Right click on the background of diagram
2. Select "Presentation Options > Entity Columns Display Options > Show Column User Type" from the popup menu.
Best regards,
Jick Yeung
written by M Zeino on July 27, 2012
Hi!
Does anyone know how to implement "IS-A" in ERD using VP?
written by sohaib on February 10, 2013
how to create one-to-one optional in ERD through uml pairadigm
written by Jick Yeung (VP) on February 14, 2013
Hi sohaib,
You can set the cardinality via the specification of a relationship. Try this: Create a one-to-one. Right click on the connector and select Open Specification... from the popup menu. In the specification window, select "Zero or One" as the Cardinality of the to-side.
Best regards,
Jick Yeung
written by Richa Nigam on May 28, 2013
I am asking again & again how to create database for .net & mysql because everywhere u r creating database for java because i am not getting what is to be select in adapter & driver place when i am going through tools then database configuration (after creating ER Diagram) & i sent alot of mails regarding this but no body didnt reply for this & same for how to create class diagram using ER diagram.
written by Rain Wong on May 28, 2013
Hi Richa,
You can simply press the Green Arrow button next to the Driver file and Adapter file field to let VP download the files for you. Please make sure you have run the application with Admin permission (right click on the executable and select Run as administrator), and also with proper proxy server setting specified (if you need proxy for access Internet).
BTW, we seems only receive 2 email request from you. As I know our support team are checking with you about your other requests. Feel free to contact us for any questions.
Best regards,
Rain Wong