Question: What percentage of users want to use which DB? 
SQL:
SELECT Databases.name, COUNT(Databases.id) * 100.0 / (SELECT COUNT(DISTINCT Response_id) FROM Response_DatabaseWantToWorkWith) FROM Databases JOIN Response_DatabaseWantToWorkWith ON Response_DatabaseWantToWorkWith.Databases_id = Databases.id GROUP BY Databases.id
SELECT Databases.Name AS "Database", COUNT(*) * 100.0 / (SELECT COUNT(*) FROM Responses) AS "Percentage" FROM Response_DatabaseWantToWorkWith JOIN Databases ON Response_DatabaseWantToWorkWith.Databases_id = Databases.id JOIN Responses ON Response_DatabaseWantToWorkWith.Response_id = Responses.id GROUP BY Databases.Name