1. First Principles of Business Intelligence with Power BI

Before you touch a single Power Query step, you need four foundations: the pipeline every Power BI solution follows, the shape a good analytical model takes, the two languages that act on that model at different moments, and the idea of context that decides what every number on a report actually means. Every PL-300 objective is a variation on these four ideas. A "wrong total" question is really a context question; a "minimize model size" question is really a modeling question; a "where should this logic live" question is really an M-versus-DAX question. Learn them here and the later phases become recognition rather than memorization.

Think of the four foundations as a map: every later objective sits somewhere on it, and locating a question on the map is half of answering it.

⚠️ Exam Trap: Many wrong answers fix a problem at the wrong stage of the pipeline, such as writing DAX to repair dirty data that Power Query should clean once, upstream of every report.