The M query language includes hundreds of functions and several books have been written about to its application. The greater purpose of this chapter is to understand M queries in the context of a corporate Power BI solution that primarily leverages an IT-managed data warehouse. As shown in the examples shared in the M Queries section earlier, the combination of a mature data warehouse and a layer of SQL view objects within this source may eliminate any need for further data transformations. However, Power BI Dataset designers should still be familiar with the fundamentals of M queries and their most common use cases, as it's often necessary to further extend and enhance source data.
The following sections demonstrate three common data transformation scenarios that can be implemented in M. Beyond retrieving the correct results, the M queries also generate SQL statements for execution by the source system via query folding, and comments are included for longer-term maintenance...