Sooner or later, you may find yourself working directly with the Power Query M formula language. Tools like Microsoft Excel’s Get & Transform Data and Microsoft Power BI provide point-and-click interfaces allowing you to build data transformation sequences which behind-the-scenes are implemented in Power Query M. However, these query editors can’t do everything you might need. Sometimes direct editing and authoring of M is required.
Search the Internet and you’ll find many examples showing how to use this language to solve one problem or another but little is out there describing the syntax and paradigm of the language itself. A limited knowledge of these details may be insignificant when simply copying and pasting samples and editing variable and column names. Move beyond this to weaving and writing your own solutions directly in Power Query M and a solid understanding of the language’s syntax, rules and capabilities becomes most helpful.