Working with Group By

One of the most valuable and advanced techniques in data modeling is creating summary tables. In many scenarios, using this method is very beneficial. We can use this method to manage our Power BI file's size; it also improves performance and memory consumption. Summarization is a known technique in data warehousing where we want to change the granularity of a fact table. But in Power Query, there are other cases where we can use the Group By functionality to cleanse data. Nevertheless, from a data modeling point of view, we summarize a table by grouping by some descriptive columns and aggregating the numeric values.

Let's go through a scenario and see how the Group By functionality works.

Note

The Group By operation changes the table's structure. To keep the Internet Sales table unchanged for the future scenarios in this chapter, we will reference the Internet Sales table and name it Internet Sales Summary. We'll use that table in...