A DirectQuery dataset is limited to a single data source and serves as merely a thin semantic layer or interface to simplify the report development and data exploration experience. DirectQuery datasets translate report queries into compatible queries for the data source and leverage the data source for query processing, thus eliminating the need to store and refresh an additional copy of the source data.

A common use case of Power BI and SSAS Tabular DirectQuery datasets is to provide reporting on top of relatively small databases associated with OLTP applications. For example, if SQL Server 2016 or later is used as the relational database for an OLTP application, nonclustered columnstore indexes can be applied to several tables needed for analytics. Since nonclustered indexes are updateable in SQL Server 2016, the database engine can continue to utilize existing indexes to process OLTP transactions, such as a clustered index on a primary key column while the nonclustered columnstore index will be used to deliver performance for the analytical queries from Power BI. The business value of near real-time access to the application can be further enhanced with Power BI features, such as data-driven alerts and notifications.