Many times, due to complicated patterns on the design of databases, our mind isn't enough to remember complex designs, that's why normally a lot of database designers use database design tools that make this pretty easy to do. However, you won't be able to work everytime with tools that you always use like SQLYog or others to achieve this because you are not at home or you're working on a public computer. An online solution would be pretty nice right ? That's why the WWW SQL Designer project has been created with promising results.
This project is distributed under the New BSD license and you can test it online here !
Contribute to the project
The official source code is hosted in Github, so don't forget to take a look and star the repository. As the repository is public, you will be able to even create pull requests.