All,
I can run the SQlite browser against library.db and extract some interesting statistics.
I am also aware of this statistics package with sql statements.
It would be nice to query statistics inside darktable, be able to run set up queries in a simple way and run them against the database.
I have looked around the api documentation and various lua scripts, and could very well have missed what I am looking for. If you know of an example showing how to get to the library.db via embedded lua and be able to execute sql statements, I would be grateful for a link/hint 
/Per