At the moment (July 2015), SQL Server Analysis Services (SSAS) data has the widest range of connection options in Power BI. This is a good thing, but the flip side of this is that great power tends to lead to complexity. In this post, I hope to clarify some of the complexity, and clearly spell out the different data connection options for it.
To begin with, SSAS running in Tabular mode is currently the only on-premises data source that supports direct query data. When operating in this fashion, at no point is data persisted or cached in the Power BI Service. Reports exist in the service, but every interaction with the reports goes back to the SSAS on-premises server for execution, and the results are streamed live back through the service to the requesting client. Operating in this mode has several advantages. Since you are maintaining your own SSAS server, there are no total capacity limits on your data models, compared to the 250 Mb limit on most models in the Power BI service. All data is stored on-premises, so it does not count against your total overall storage limits (10 GB for Pro users). Data is served up in real time, so there is no need to wait for a refresh process. Finally, since data is persisted on-premises, there are also no data sensitivity or sovereignty issues. You can use the cloud based Power BI services, and still maintain a policy of having no sensitive data stored in the cloud, or out of country.
There is of course a cost to all of this flexibility. Live connections require a Power BI Pro license (currently $9.99 US/user/month), and anyone consuming these reports must have such a license. You must of course maintain an SSAS server, which has its own added cost, and you must also install and maintain an SSAS Connector somewhere within your environment. Power BI uses Azure Active Directory for authentication, while SSAS uses only Windows authentication. Therefore, your directory needs to be federated with AAD (same as Office 365 directory federation) in order to use it, although this excellent post by Greg Galloway describes a workaround for test scenarios.
Of course, direct query is not the only way to work with SSAS data. SSAS data can also be loaded into a data model, and refreshed on a periodic basis, like most other data sources. In this mode, the data model is loaded into the Power BI service, and is refreshed periodically through the Power BI Personal Gateway. This approach is common to all on-premises based data sources.
On the tooling front, there are currently three different tools that can be used to connect to SSAS data, with only one of them supporting both the direct query and imported modes. Let’s walk through each one.
Excel can connect to SSAS three different ways. You can use the traditional Data – From Analysis Services on the Data tab, through Power Query and through Power Pivot. The first method connects directly to the SSAS server and is unfortunately not supported at all by Power BI, even with the SSAS Connector installed.
Direct Connection to SSAS in Excel
Power Query will import data from SSAS into a workbook, a data model, or both. Power BI works with the data model, so if Power Query is used the data should be loaded into the model, and not the workbook. There is one special case where data can be loaded into the workbook, and that is if Power BI connects to the workbook and uses Excel Services instead of importing it. When a workbook, is imported, only the data model and Power Views are brought in.
Power Query SSAS Import in Excel
Finally, PowerPivot in Excel can be used directly to import data from SSAS. PowerPivot only loads data into the model, so there is no confusion here.
PowerPivot SSAS Import in Excel
Once the model is created, and visualizations created, you can either import it or connect to it in the Power BI service. Since Excel does not support the direct query mode at all, only import, the data will need to be refreshed periodically. Refresh can be performed whether the Excel file has been imported, or if it is connected through Excel Services. Reports created in Excel can work with SSAS whether it is running in Tabular Mode, or Multidimensional (OLAP) mode.
Power BI Desktop
Power BI Desktop is a client application that allows you to import, or connect to live data, create and edit data models, and produce reports. You can use it to connect to Analysis Services in both live query mode, and in imported mode. Once launched, simply select “Get Data” and then select SQL Server Analysis Services Database and click “Connect”.
The next dialog is important to determine the behaviour of your Power BI Report. Here you enter the name of the SQL Server Analysis Services Server that you need to connect to, and then the way that you can connect. You MUST be able to connect to this from your client – communication does not flow through the SSAS Gateway at this point.
SSAS Connection Options in Power BI Desktop
The first option will connect to the SSAS using Live Query Mode. IN order to use this option from Power BI, you will need to be using the SSAS Gateway somewhere on your premises. The second option will import the data into a model in the same manner that Excel does. This mode will NOT require the SSAS Gateway, but it WILL require the Personal Gateway in order to keep the data in the Power BI model refreshed.
In addition, the Live Query approach will ONLY work with SSAS Servers running in Tabular mode. If your SSAS server is running in Multidimensional mode, the second option (import) is your only choice.
Once the report is created, it can be published to the service using the publish button, or the created .pbix file can be imported via the same mechanism as Excel.
Power BI User Interface
If you have an SSAS Connector registered somewhere within your organization, you can create a connection to it directly from the Power BI user interface. The Power BI interface can only connect to Analysis Services in Live Query mode, imported models must be created using either Excel or Power BI Desktop.
In order to browse an on-premises SSAS server, first Select “Get Data” in the Power BI user interface, then select “Get” in the Databases section. Then select the “SQL Server Analysis Services” option, and click “Connect”. When you do, you’ll be presented with a screen containing all SSAS servers that have been registered with your organization.
SSAS Servers Registered with Power BI
Click on the one that you wish to connect to, and you’ll be presented with a list of data models to connect to.
SSAS Model Selection
Once selected, the model will appear in the list of Datasets in Power BI.
Clicking on it will allow you to browse the model, and to start building reports. Since the Dataset uses Live Query, there is no need to schedule any sort of a refresh, your reports will always be as fresh as the data on SSAS.
We can summarize the various SSAS connection options for the various Power BI design tools in the following table.
|Design Tool||Live Query||Imported|
|Excel||No||Power Query Load to ModelPower Pivot|
|Power BI Desktop||Yes (Tabular mode)||Yes (all modes)|
|Power BI UI||Yes (Tabular mode)||No|
I expect some of this information to change over time, but at the initial launch of Power BI V2, this is where Analysis Services fits in.