I fairly commonly find myself in a situation where I would like to display one label for certain features and another for other features in the same layer. QGIS doesn’t have an official way to split labels up into categories, and until now I’d resorted to having two layers to render otherwise identical features.
Over the last week I’ve started a new project, GTFSrDB, which allows you to connect GTFS-realtime with an SQL database, allowing app developers to use realtime data through SQL, just as easily as they use static data.
When you load GTFS data into PostGIS using gtfsdb, you can’t access that data in QGIS because the tables don’t have a primary key in int4 format (the primary key is in text format).