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ssaspowerbi-desktopssas-tabularmultidimensional-cube

Are tabular and multidimensional models built the same way?

I'm having a real hard time understanding what the difference is between a tabular vs multidimensional model.

Don't both use dimensions and fact tables?

Can't both have a star or snowflake schema?

Don't both have measures and calculated columns?

What is the difference?

Also, if I'm using Power BI and I connect to SQL Server instead of SSAS, I can still do my thing with it. Why is SSAS needed for tabular models if you can just do it in SQL Server?

Solution

  • Don't both use dimensions and fact tables?

    Nope. Multidimensional uses Attribute Hierarchies and Measure Groups. Tabular uses Tables, and has no built-in notion of what a "fact" or "dimension" is.

    Can't both have a star or snowflake schema?

    Yes. And Tabular can have other designs as well. Tabular models can have single-table, or more normalized schemas, although using a star or snowflake design is generally considered a best-practice.

    Don't both have measures and calculated columns?

    MD does not have calculated columns. See Comparing tabular and multidimensional solutions

    Also, if I'm using Power BI and I connect to SQL Server instead of SSAS, I can still do my thing with it.

    Nope. Power BI always uses a Tabular or Multi-Dimensional model. When you connect to SQL Server with Power BI you are creating a Tabular model, and either Importing the data into memory, or creating a DirectQuery model (or a hybrid). In either case there is still a Tabular Model created, either embedded in the .PBIX or in a SSAS/AAS server.