For DirectQuery datasets, every M query is folded to exclusively utilize the resources of the single data source. Therefore, certain M functions and query logic that lack an equivalent SQL expression for the given data source, such as Oracle or Teradata, are not supported. In these scenarios, the dataset designer can develop alternative M queries that produce the same target data structure and are supported by the source system or implement the necessary logic within the layer of SQL views supporting the dataset.
An additional and fundamental limitation to the scope of M queries for DirectQuery datasets is the impact on query performance and user experience. Since the SQL statements representing M queries must ...
