Creating an advanced list based on the table in another field

If I understand correctly, you want two dropdown boxes. The first dropdown box will contain all your tables, and the other will contain the rows from the table you selected.

I got a demo working locally. As long as you know the table you're selecting will have the two fields you wanted, "num, title", you should get a working dropdown or you will get a mysql error when selecting that table.

The solution I came up with is this,

I created a field with type "list". The field label and name can be whatever you want. I selected "pulldown" for Display As. List Options was the advanced MySQL Query option.

I used your same query for displaying the table names.

SELECT REPLACE(TABLE_NAME, '<?php echo $TABLE_PREFIX;?>', '') FROM information_schema.`TABLES` where TABLE_SCHEMA = '<?php echo $GLOBALS['SETTINGS']['mysql']['database'];?>' AND TABLE_NAME like '<?php echo $TABLE_PREFIX;?>_%' ORDER BY TABLE_NAME

For Input Validation, I selected the checkbox for "User may not leave field blank".

The second field I created was also of type "list" and it was a pulldown. Using the advanced list options query, I used the following code

<?php
if($ESCAPED_FILTER_VALUE): ?>
SELECT num, title FROM <?php echo $TABLE_PREFIX.$ESCAPED_FILTER_VALUE; ?>
<?php
else:
?>
SELECT "Please select value in field above...";
<?php
endif;
?>

In the Advanced Filter dropdown, I selected the first field so it refreshes upon the first dropdown list being changed. Let me know if this make sense or if you have any other questions.