At http://www.cfsolutions.de/qb/ you will find a first beta of a visual sql query builder plugin. It is possible to drag and drop tables to the left area and to define joins between the tables via drag and drop. I have startet generating the resulting sql for mysql.
The source is not encrypted anymore. So feel free to use the source as it is.
@another_i It seems to be a obusfactor problem. The non obusfactored version is running fine with chrome. At the moment the public beta is obusfactored until I have made a decision wich license I want to use. Try it with firefox to test the plugin right now.