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.
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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):