I'm really new to QGIS coding and I'm having a hard time finding (especially) the api classes/functions to carry out actions of the Query Builder window.
I'm basically trying to do this:
Iterate from n=1 to 200...
Query layerA where field_id = n
Query layerB where field_id = n
Query layerC where field_id = n
Save as img_n.png
Pretty simple, I think, but it has become a real pain to do by hand in the GUI.