Tag Archives: Role-playing dimension

Role Playing Dimensions in Power BI

In this post I want to explain how to handle role playing dimensions in Power BI. I wrote an article awhile ago regarding role playing dimensions in SSAS Tabular which is valid for Power BI Desktop. But, in this post I show you two new alternative ways to handle role playing dimensions without importing tables, for instance DimDate,  into the Power BI model several times. You also don’t have to create database views on your source database. I show you how to manage this in both DirectQuery and Import modes when connecting Power BI Desktop to a SQL Server database.

I used AdventureWorksDW2016CTP3, but, you can use any other versions of AdventureWorksDW database or you can mimic the process to your own model.

Note: If you are designing a star schema for your data warehouse you can easily create a Date dimension as explained here.

The idea is to manage role playing dimensions in Power BI Desktop itself in the easiest way possible.

Role Playing Dimensions in Import Mode

  • Open Power BI Desktop
  • Get data
  • Select “SQL Server”
  • Enter the server and database names then click OK

Power BI SQL Server Connection

  • Select DimDate and FactInternetSales from the list then click “Load”
  • “Import” mode is selected by default. Click OK

Power BI Connection Settings

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Side-by-side Role-Playing Dimensions In Power BI

Role-playing dimension is one those concepts that is discussed a lot from time to time. I also posted an article about implementing role-playing dimensions in Tabular models. In one my recent posts I used the same concept to implement role-playing dimensions in Power BI. So in this post I’m not going to explain role-playing dimensions in Power BI again.

In some cases you need to have especial calculated measures based on the roles you have in a fact table. One the most common role-playing dimensions is Date dimension. Consider you have to show Internet Sales Amount by Order Date, Due Date and Ship Date in a single chart in your report. In this case, having 3 different date tables won’t help us to achieve the goal. Again I refer to my previous post where I said I keep the original Date table in the model for a reason.

Defining a new Calculated Measure in Power BI Desktop

Basically, what I’m going to explain in this post is using inactive relationships between FactInternetSales table and the DimDate dimension by adding a new Calculated measure. In this case, we’ll be able to show Sales Amount by different roles, well, dates in this sample in a single chart.

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Role-playing Dimension in SSAS Tabular Models

First of all I’d like to explain what a Role-playing dimension actually means. Then I’ll express the way you can implement it in a SSAS tabular model.

When you link a dimension to a fact table several times for logically distinctive roles you’re using a role-playing dimension.

The key points are:

1.       You are linking a fact table to a dimension multiple times. The relationships are defined by linking multiple foreign keys in the fact table to a single key in the dimension table.

2.       Each linkage represents a single role or concept

The most popular role-playing dimensions are DimDate and DimTime.

NOTE: The sample is from Microsoft “AdventureWorksDW” for SQL Server 2012 and might be different from your own data warehouse design.

For instance, in a sales system that you have something like FactInternetSales fact table which has several links, or relationships, to a DimDate or DimAddress for distinct concepts like “Order Date”, “Ship Date” and “Due Date”.

As you see, all of the above columns obviously represent different meanings of date. In the data warehouse design you’ll see something like this:

role-playing dimension 01

Although this is absolutely OK in the relational database layer, but, this sort of relationship is NOT permitted in the tabular model, so what should we do?

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