Connect to SSAS Multidimensional Models in Power BI Desktop
With Power BI Desktop, you can access SSAS Multidimensional models, commonly referred to as SSAS MD.
To connect to an SSAS MD database, select Get Data > Database > SQL Server Analysis Services Database as shown in the following image:
SSAS Multidimensional models in Live connection mode are supported in both the Power BI service and in Power BI Desktop. You can also publish and upload reports that use SSAS Multidimensional models in Live mode to the Power BI service.
Capabilities and features of SSAS MD
The following sections describe features and capabilities of Power BI and SSAS MD connections.
Tabular metadata of multidimensional models
The following table shows the correspondence between multidimensional objects and the tabular metadata that's returned to Power BI Desktop. Power BI queries the model for tabular metadata, and based on the returned metadata, runs appropriate DAX queries against Analysis Services when you create a visualization such as a table, matrix, chart, or slicer.
|BISM-Multidimentional object||Tabular Metadata|
|Dimension attributes (Keys), Name||Columns|
|Measures without associated Measure Group||Within table called Measures|
|Measure group -> Cube dimension relationship||Relationship|
Measures, measure groups, and KPIs
Measure groups in a multidimensional cube are exposed in Power BI as tables with the ∑ sign beside them in the Fields pane. Calculated measures that don't have an associated measure group are grouped under a special table called Measures in the tabular metadata.
In a multidimensional model, you can define a set of measures or KPIs in a cube to be located within a Display folder, which can help simplify complex models. Power BI recognizes Display folders in tabular metadata, and shows measures and KPIs within the Display folders. KPIs in multidimensional databases support Value, Goal, Status Graphic, and Trend Graphic.
Dimension attribute type
Multidimensional models also support associating dimension attributes with specific dimension attribute types. For example, a Geography dimension where the City, State-Province, Country, and Postal Code dimension attributes have appropriate geography types associated with them are exposed in the tabular metadata. Power BI recognizes the metadata, enabling you to create map visualizations. You'll recognize these associations by the map icon next to element in the Field pane in Power BI.
Power BI can also render images when you provide a field containing URLs (Uniform Resource Locator) of the images. You can specify these fields as ImageURL type in SQL Server Data Tools (or subsequently in Power BI), and its type information is provided to Power BI in the tabular metadata. Power BI can then retrieve those images from the URL, and display them in visuals.
Multidimensional models support Parent-child hierarchies, which are presented as a hierarchy in the tabular metadata. Each level of the Parent-child hierarchy is exposed as a hidden column in the tabular metadata. The key attribute of the Parent-child dimension is not exposed in the tabular metadata.
Dimension calculated members
Multidimensional models support creation of various types of calculated members. The two most common types of calculated members are the following:
- Calculated members on attribute hierarchies and not sibling of All
- Calculated members on user hierarchies
Multidimensional models expose calculated members on attribute hierarchies as values of a column. There are a few additional options and constraints while exposing this type of calculated member:
- Dimension attribute can have an optional UnknownMember
- An attribute containing calculated members cannot be the key attribute of the dimension, unless it is the only attribute of the dimension
- An attribute containing calculated members cannot be a parent-child attribute
The calculated members of user hierarchies are not exposed in Power BI. Rather, you will be able to connect to a cube containing calculated members on user hierarchies, but you won't be able to see calculated members if they do not meet the constraints mentioned in the previous bulleted list.
Multidimensional models support dimension and cell level security by way of Roles. When you connect to a cube with Power BI, you are authenticated and evaluated for appropriate permissions. When a user has dimension security applied, the respective dimension members are not seen by the user in Power BI. However, when a user has a cell security permission defined, where certain cells are restricted, then that user cannot connect to the cube using Power BI.
Limitations of SSAS Multidimensional Models in Power BI Desktop
There are certain limitations to using SSAS MD:
- Servers must be running SQL Server 2012 SP1 CU4 or later versions of Analysis Services for the Power BI Desktop SSAS MD connector to work properly
- Actions and Named Sets are not exposed to Power BI, but you can still connect to cubes that also contain Actions or Named sets and create visuals and reports.
Supported Features of SSAS MD in Power BI Desktop
The following features of SSAS MD are supported in Power BI Desktop:
- Consumption of the following elements are supported in this release of SSAS MD (you can get more information about these features):
- Display folders
- KPI Trends
- Default Members
- Dimension Attributes
- Dimension Calculated Members (must be a single real member when the dimension has more than one attribute, it cannot be the key attribute of the dimension unless it is the only attribute, and it cannot be a parent-child attribute)
- Dimension Attribute types
- Measures (with or without Measure groups)
- Measures as Variant
- Dimension security