Question: What percentage of users want to keep using their current DB by DB? 
SQL:
SELECT Databases.name, COUNT(Databases.id) * 100.0 / count2 FROM Databases JOIN Response_DatabaseHaveWorkedWith ON Response_DatabaseHaveWorkedWith.Databases_id = Databases.id JOIN Response_DatabaseWantToWorkWith ON Response_DatabaseWantToWorkWith.Response_id = Response_DatabaseHaveWorkedWith.Response_id AND Response_DatabaseWantToWorkWith.Databases_id = Databases.id JOIN (SELECT Databases.name AS name2, COUNT(Databases.id) AS count2 FROM Databases JOIN Response_DatabaseHaveWorkedWith ON Response_DatabaseHaveWorkedWith.Databases_id = Databases.id GROUP BY Databases.id) ON Databases.name = name2 GROUP BY Databases.id