Concepts
Core ideas and patterns in the Power Query M language. Understanding these concepts will help you write faster, more maintainable queries.
Custom Functions
How to create reusable custom functions in M to modularize your code, reduce duplication, and build shareable function libraries.
The each Keyword
Understanding each as shorthand for single-parameter functions, and how bracket notation accesses row fields.
Error Handling
How to handle errors gracefully in M using try, otherwise, and error records.
Lazy Evaluation & Table.Buffer
How M evaluates expressions on demand, and when you need Table.Buffer to force eager evaluation.
MissingField Handling
How to make your queries resilient to upstream column changes using MissingField options.
Query Folding
How Power Query translates M steps into native data source queries for dramatically better performance.
Type System
How M's type system works — primitive types, nullable types, type annotations, and their impact on performance.