Clarification on Direct Query

[gazpage]

Can anyone point me to a summary of how Direct Query works? In particular I am interested in the difference between querying a SQL database and a SSAS Tabular model.

Presumably if I Query a SQL database then I need to create the measures in Power BI as I would normally. If querying SSAS, does Power Bi just pull in the measures directly with no modelling at the Power BI end? If SQL server, how are more complex DAX measures calculated if they use capabilities not in SQL?

Thanks in advance

 

[Matt Allington]

Presumably if I Query a SQL database then I need to create the measures in Power BI as I would normally.

yes, but there are limitations including you don't get the performance of a tabular model and also you can't use the time intelligence functions.

If querying SSAS, does Power Bi just pull in the measures directly with no modelling at the Power BI end?

yes

If SQL server, how are more complex DAX measures calculated if they use capabilities not in SQL?

there are limitations to this approach and there are things you can't do. Personally I never use it.

This is good https://powerbi.microsoft.com/en-us/documentation/powerbi-desktop-use-directquery/

 

[gazpage]

Very clear and helpful. Thank you.