I'm learning DB design and looking for some tools, preferably open source software, that could help go from an ERD to a DATABASE and vice versa.
For the record, the database i'm using is MySQL.
Since you're using MySQL, you might want to take a look at MySQL Workbench.
It might not quite display the ERDs you're expecting but it gets the job done.
And it does have an import feature. I have only used it to import SQL files but apparently you can import from existing MySQL databases.
Also, a long time ago I found the following tools; but were not quite useful to me back then (perhaps they've matured by now):
Generate ERD with PHPMyAdmin is also a better option. PHPMyadmin added this functionality from version 3.4
detail step to generate ERD : http://goo.gl/0z3vFE
You can refer to PHPMyAdmin documentation for more info: http://www.phpmyadmin.net/documentation/#pmadb
Ideas for paid products anyway....
You could also check out IBM Data Studio as its free. I believe it does ER to DDL and it supports more than just IBM databases.