How do I avoid the maintenance screen on database errors?
If you have a serious / fatal database error, you're probably not seeing the 'maintenance page' but the db_offline page which usually displays errors direct to screen. What kinds of database errors are you experiencing?

Assuming your site is not in maintenance mode, few things you can check and set:


Check the settings under admin/config/development/logging and make sure you have it set to display 'all messages' 
Make sure you have php set to display errors -- you can add the following in your settings.php file to increase your error_reporting level: 




error_reporting(-1);
$conf['error_level'] = 2;
ini_set('display_errors', TRUE);
ini_set('display_startup_errors', TRUE);