Category: Business Intelligence – BI

BISM Tabular, Business Intelligence - BI, Data Warehousing - DW, SQL Server Analysis Services - SSAS

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. Do you want to see how to implement Role Playing Dimensions in Power BI, Click here and here.

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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BISM Tabular, Business Intelligence - BI, SQL Server, SQL Server Analysis Services - SSAS, T-SQL

How To Implement a Composite Key In SSAS Tabular Model

As you might know SSAS tabular models do not support composite keys so you always must have just one column to make a unique row through the whole table. This is such a pain especially when you are new to the tabular models and don’t have that much detail information about it. So when you import some tables with existing relationships based on composite keys, the Table Import Wizard will ignore those relationships.

So what should we do to solve the problem?

The solution is to combine the values of the composite keys. 

Here is how you can do the job?

·         Creating a view on top of the source tables:

1.  If you’re using SQL Server 2012 and above you can use the “concat” function to combine the values. The function combines several expressions regardless of their data types. So you can use it like this select CONCAT (1, 1.22100001,‘First’) SQL2012 and the result would be something like this

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2.  If you’re using earlier versions of SQL Server then you need to mind the data types. So for the above sample the SQL code would be select cast(1 as char(1)) + cast(1.22100001 as char(10))+‘First’ SQL2008 . As we expect the result is the same.

·         Adding a new computed column to all tables involved in SQL Server before importing the tables to the tabular model

·         Adding a new calculated column to all tables involved after importing the tables to the tabular model

As a quick note, you’ll need to remove the existing relationships imported from SQL Server and create the new relationship based on the combined keys.

Easy peasy!

BISM Tabular, Business Intelligence - BI, SQL Server Analysis Services - SSAS

Resolving “Object reference not set to an instance of an object.” Error When Deploying your Tabular Model

You’ve changed something in your Tabular model and you’re facing an ugly “Error: Object reference not set to an instance of an object.” message, don’t rush. Just go to the table you’ve made some changes and click on “Partitions” button.

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Then click “Refresh Preview” button and click OK.

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All done!

BISM Tabular, Business Intelligence - BI, SQL Server Analysis Services - SSAS

How to Automate SSAS Tabular Model Processing

You are working on a BI project that involves SSAS Tabular model. As you cannot process the model manually you need to develop a solution to process the model automatically. There are two scenarios here:

  1. You have an up and running SQL Server Integration Services (SSIS) instance: In this case you can build a SSIS package to process the Tabular Model.
  2. You do not have an SSIS instance ready on the server: So you need to create a SQL Server Agent Job.

In this post I’m expressing easy ways to solve the problem based on the above scenarios.

Using SQL Server Integration Services to Process SSAS Tabular Model

Follow the steps below:

  1. Create a new SSIS project using (SQL Server Data Tools) SSDT
  2. Right click on the “Connection Managers” area and select “New Analysis Services Connection”image

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