Two things:
After you alter question in the database, you need to purge Moodle caches (specifically the Question definition cache). Admin -> Development -> Purge caches.
- Make sure you know the right thing to put in the database. Best way to do that is to edit one question through the Moodle UI. Then check that the quesition is actually working the way you want as a result of that edit. Then look at what data is stored in the database for that, and use that value for the other questions.