Hi Christian,
This may be possible- and no need to upgrade- take a look at the "Configurable Reports" Plugin for Moodle (including 1.9) it gives you an array of configurable predefined querys and also an 'SQL' report type, when selecting SQL- there are a load of contributed SQL reports that you can simply copy and paste in to get the results- if there isnt quite what your looking for at least it will give you an idea of the variables you need.