SUMMARIZE [DAX Virtual Table Series - Ep. 5]

In this Pragmatic Works training video, Jeremiah Hersey continues his six-part series on virtual tables in DAX by focusing on the SUMMARIZE function. He explains that SUMMARIZE is one of the original DAX functions used to create summary tables by grouping data based on specific columns. While the function remains useful, Jeremiah makes an important recommendation throughout the lesson: although SUMMARIZE can technically add columns to a summary table, it is not the best approach for doing so.

Jeremiah demonstrates the function inside Power BI Desktop by creating a new calculated table. His goal is to show how SUMMARIZE works, how it groups data, and why users should be careful when using it to extend a summarized table with additional calculated columns. The lesson is practical, direct, and designed to help Power BI users better understand how this classic DAX function fits into modern modeling practices.

What the SUMMARIZE Function Does

Jeremiah explains that the SUMMARIZE function creates a new table by taking an existing table and grouping it by one or more specified columns. In the example shown in the video, he summarizes the Sales table and groups the results by Product Color from the Product table. This creates a table that organizes sales-related information based on color categories.

This type of summarization is useful when users want to reduce detailed transactional data into a more readable, grouped format. Rather than reviewing every row in the Sales table, they can look at a cleaner output organized by a meaningful business attribute.

Demonstration in Power BI Desktop

During the demonstration, Jeremiah creates a new table and names it Summarize Table. He then begins writing the DAX expression using the SUMMARIZE function. The key steps in his example include:

• Selecting the Sales table as the input table to summarize
• Grouping the data by Product[Color]
• Adding a sales-related column to show that the function allows extra expressions

Although the function supports this structure, Jeremiah clearly warns that adding columns directly inside SUMMARIZE is not recommended. He repeats this guidance multiple times to make sure viewers understand the best practice.

Why Adding Columns with SUMMARIZE Is Not Recommended

One of the most important takeaways from the video is Jeremiah’s explanation that SUMMARIZE should primarily be used for grouping data, not for building enriched summary tables with additional calculated columns. While the syntax allows users to define extra columns, this older pattern is not considered the preferred method.

Instead, Jeremiah recommends two better alternatives:

1. Use the SUMMARIZECOLUMNS function, which is designed for creating summary tables with additional columns
2. Use a combination of ADDCOLUMNS with SUMMARIZE when needed

He notes that the next video in the series will focus on SUMMARIZECOLUMNS, which provides a more appropriate way to add columns to a summary table. This creates a strong connection between the current lesson and the next part of the series, helping learners build a more complete understanding of DAX virtual table functions.

Data Lineage and Filtering Behavior

Jeremiah also points out that the summarized table preserves data lineage. This means the grouped data still maintains a relationship to the original source data, allowing filtering behavior to continue working properly. In the example, the summarized results by product color still retain the ability to filter and interact meaningfully with the related data model.

This is an important concept in DAX because it shows that summary tables are not just static outputs. When created correctly, they can still participate in the broader logic of the model and support further analysis.

Key Learning Points from the Video

• SUMMARIZE is one of the original DAX functions for creating grouped summary tables
• It allows users to group a table by one or more columns
• It can technically add columns, but this is not the recommended practice
• SUMMARIZECOLUMNS is the better option when adding calculated columns to a summary table
• ADDCOLUMNS combined with SUMMARIZE is another acceptable approach
• Summary tables created with SUMMARIZE can preserve data lineage for filtering

Conclusion

In this lesson, Jeremiah Hersey gives Power BI users a practical introduction to the DAX SUMMARIZE function and clarifies where it fits in today’s best practices. The video helps learners understand that SUMMARIZE is still valuable for grouping data, but it should be used carefully. Its ability to add columns may seem convenient, but more modern and reliable approaches exist for that task.

For anyone learning DAX virtual tables, this video offers a strong foundation in how SUMMARIZE works and prepares viewers for the next step in the series, where Jeremiah introduces SUMMARIZECOLUMNS as the preferred method for building more complete summary tables.

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