Just out of curiosity why are you using a multi value field and what are the contents of that field for?
And I think you may want to invest some time in rethinking your structure.
For instance your 'round' is a mix of difficulty level and categories as far as I can tell
For each question you want to be able to identify
1. Difficulty Level (Easy, Medium (maybe), Hard)
2. Theme (Geography, Pop Culture, Current Events, World History, etc.) Where a particular question could fit multiple themes
3. Category (Countries, World Capitals, Rivers, Mountains, etc.) Where a particular question could fit multiple categories
4. Sub Category (European, North American, Asian, African, etc.) Where a particular question could fit multiple sub categories
Then when you run your code it should be much easier to pick out your possibles than your current structure (though yours is close)
In terms of a table structure you'd need a table to hold:
Question Theme - A Junction table between your question set and the theme(s) of each question
Question Category - A Junction table between your question and the category(ies) of each question
Question Sub Category - A junction table between your question and the sub cateogry(ies) of each question
So for instance let's say you had this in your QUESTIONS table
Code:
tblDifficulty
D_ID D_Text
1 Easy
2 Medium
3 Hard
Q_ID D_ID Q_Text
1 2 What US state borders only one other?
You would set the difficulty of this question on the QUESTIONS table
in your QUESTIONTHEME table you might have
Code:
tblTheme
T_ID T_Text
1 Geography
2 US States
3 I'm the Only One
4 European
5 African
tblQuestionTheme
QT_ID Q_ID T_ID
1 1 1
2 1 3
3 1 2
Where the question may fit geography, US States, I'm the only one themes.
A similar arrangement for both the category and subcategory. This would give you the most flexibility in your question gathering.
Lastly, are you going to put a moratorium on asking a question for x amount of days, months, weeks (whatever) after you use it to prevent the same question from being used on consecutive sessions?