Press "Enter" to skip to content

Star Schemas and Power BI Go Together

Marco Russo and Alberto Ferrari explain why star schemas make so much sense for Power BI:

Why should I have products, sales, date and customers as separate tables? Wouldn’t it be better to store everything in a single table named Sales that contains all the information? After all, every query I will ever run will always start from Sales. By storing everything in a single table, I avoid paying the price of relationships at query time, therefore my model will be faster.

There are multiple reasons why a single, large table is not better than a star schema. Here anyway, the focus is strictly on performance. Is it true that a single table is faster than a star schema? After all, we all know that joining two tables is an expensive operation. So it seems reasonable to think that removing the problem of joins ends up in the model being faster. Besides, with the advent of NOSQL and big data, there are so many so-called data lakes holding information within one single table… Isn’t it tempting to use those data sources without any transformation?

Read on to see why this is not the case.