I have no idea what the future of MySQL might be under Oracle's ownership, but as long as it lasts this is the most incredible development tool and for that matter a pretty good low volume production database.
Even more impressive than the MySQL database itself is the MySQL Workbench which can also be freely downloaded from MySQL.Org. I have been using data modeling tools since 1980. Many of these tools cost as much as $20,000 per workstation. Others were in the $1500 to $2000 range. ADW from Knowledgeware was the most expensive and consisted of four separate components priced at $20k per workstation each.
MySQL Workbench does all of the data modeling that these old expensive tools did and includes both forward and reverse engineering tools. You can quite simply point the MySQL Workbench at an existing MySQL database and it will reverse engineer the database into an ER Diagram. You can modify the model and forward engineer it back to your physical environment.
It took me about 5 minutes to download XAMPP (for my MAC) which isa complete MySQL test environment, then MySQL Workbench, install them and have a complete database development environment running on my MacBook with PHP.
This is absolutely amazing and provides all of the benefits of much more expensive modeling tools.
Just one more example of Open Source providing leadership in todays world.