Marco Russo

Yesterday at dataMinds.be I asked the audience how many experienced disk defrag.

I was talking about Delta/Parquet files in DirectLake. 
>50% raised their hands.

Next time, I'll ask about index rebuild on SQL Server.

We are so back.

Spoiler: 800+ pages.

Not ready to announce the official release date yet, but the third edition of The Definitive Guide to DAX has broken the 800-page barrier. 

But hey, there are many figures!

Coming soon...

User-defined functions [UDFs] in DAX (With Marco Russo) DESCRIPTION 📄In September 2025, Microsoft introduced a new feature in Power BI and in the DAX language: the ability to create user-defined functions (UDFs)....

I will be speaking live about UDF on Analytics Endeavors' channel on October 8 (morning in the US, late afternoon in Europe).
Set a reminder!

#dax #usd #live #powerbi

I don’t like the idea. Unless you include metaprogramming in DAX with proper compiler optimizations, the result of similar features would be slow slow slow performances…

Simon Sabin and I sit down and chat to answer one simple question: why bother with conferences in 2026?

In the chat, we talk about meeting peers, asking real questions, and learning from battle-tested content (not vendor demos).

Watch (or just listen to) the video: 
https://youtu.be/zwGDfL-B3jQ

I will be delivering a "Mastering DAX" Workshop in Lugano, Switzerland, from October 28-30, 2025.

This workshop is also near Northern Italy, France, and Southern Germany.

The workshop is in English. 

For more details, visit: https://www.sqlbi.com/p/mastering-dax-workshop-lugano-oct-28-30-2025/

Here is a chat with Jeroen (Jay) ter Heerdt, the product manager for DAX, talking about the new features released today: User-defined functions (UDFs) and Ca... DAX UDFs and Calendar-based time intelligence: A chat with Jay

Watch a 30-minute chat with Jay recorded at FabCon25 Europe this week.
@jaypowerbi.sky.social is the product manager of DAX.

We talk about the new features just released: User-defined functions (UDFs) and Calendar-based time intelligence.

#dax #fabconeurope25

Or should already work. Click on bugs and report the error thanks!

Yep - also check out daxlib.org/package/DaxL...

Many thing could be done, but IMHO it’s important to go GA first.

The “P” in Power BI stands for “patience” you should know that! 😎

We finally have 𝘂𝘀𝗲𝗿-𝗱𝗲𝗳𝗶𝗻𝗲𝗱 𝗳𝘂𝗻𝗰𝘁𝗶𝗼𝗻𝘀 (𝗨𝗗𝗙) in DAX!

Don't make mistakes; this is not a user data function in Fabric.

This is a new DAX feature, the most important one in the last five years.

Read/watch more:
https://www.sqlbi.com/articles/introducing-user-defined-functions-in-dax/

Read our first article and watch the video about the new calendar-based time intelligence feature in DAX and Power BI.
Helpful for Gregorian, necessary for non-Gregorian calendars.

#powerbi #dax #timeintelligence

https://www.sqlbi.com/articles/introducing-calendar-based-time-intelligence-in-dax/

There were so many things to announce at #fabconeurope that 𝗠𝗶𝗰𝗿𝗼𝘀𝗼𝗳𝘁 𝗳𝗼𝗿𝗴𝗼𝘁 to include the biggest innovations in DAX and semantic models in the last 6 years:

- 𝗨𝘀𝗲𝗿-𝗱𝗲𝗳𝗶𝗻𝗲𝗱 𝗳𝘂𝗻𝗰𝘁𝗶𝗼𝗻𝘀 (in DAX)
- 𝗖𝗮𝗹𝗲𝗻𝗱𝗮𝗿-𝗯𝗮𝘀𝗲𝗱 time intelligence

Watch out for articles on www.sqlbi.com coming in the next hour!

Introducing AI and Agentic Development for Power BI: an article that explores concepts and scenarios for integrating AI and AI agents into BI development, with specific examples for Power BI.

https://www.sqlbi.com/articles/introducing-ai-and-agentic-development-for-business-intelligence/

Maestro Alberto Ferrari in Toronto!, Wed, Aug 20, 2025, 6:00 PM | Meetup Hello everyone, We are honored and pleased to have the Fabric, Power BI and DAX international guru and the bestselling books author Alberto Ferrari. He generously accepted

If you're in Toronto, don't miss the Toronto Power Platform UG meeting on August 20, 6pm EDT.
Alberto Ferrari presents "Understanding visual calculations in Power BI" 

Follow the link for more details and to register (free!):

Yes, you can use SUMMARIZECOLUMNS in a DAX measure, BUT...

But only if you follow the best practices in this article + video.

Spoiler: Goodbye ADDCOLUMNS / SUMMARIZE - well, with some exceptions...

#dax #powerbi

https://www.sqlbi.com/articles/summarizecolumns-best-practices/

Sideways recursion in DAX calculation groups - SQLBI This article describes the sideways recursion triggered by invoking a calculation item from another calculation item, explaining why it should be avoided to

A short article about sideways recursion in calculation groups in DAX.
About why you should avoid it.

#dax #powerbi

First impressions about ChatGPT-5 with DAX.
It still doesn't "understand" the language, even though you may be lucky and get a working expression.
It is not better than other models/vendors.
But I like the English produced more than the previous versions of ChatGPT.

This article and video discuss the current state of AI tools with Power BI and how to utilize the Model Context Protocol (MCP) to interact with and control Power BI or Fabric using an LLM.

#powerbi #semanticmodel #mcp #llm

https://www.sqlbi.com/articles/ai-in-power-bi-time-to-pay-attention/

Newsletter #300 is a significant milestone for SQLBI.

I thought this was a good time to clarify SQLBI’s position on a topic we haven't discussed much yet: Artificial Intelligence (AI).

https://www.sqlbi.com/blog/marco/2025/07/28/a-few-thoughts-about-newsletter-300-and-ai/

#newsletter #sqlbi #ai

This article (with video) outlines best practices for utilizing ALLSELECTED in your DAX measures to prevent unpredictable results!

#dax #powerbi

https://www.sqlbi.com/articles/allselected-best-practices/

When should you use DISTINCT over VALUES in DAX?
Here is how to write resilient measures that survive bad data and model changes.
Article+video on SQLBI.

#dax

https://www.sqlbi.com/articles/choosing-between-distinct-and-values-in-dax/

Enjoy the videos and music that you love, upload original content and share it all with friends, family and the world on YouTube.

It needs 15 minutes to watch a video where an LLM enables you to talk with your data... for free!
Watch carefully: It does not just "work".
It's another tool - extremely sophisticated - integrated into an ecosystem.

We're living exciting times.

Learn the details about how the IF function in DAX is actually executed, analyzing also the performance in several scenarios.
Article and video available!

#powerbi #dax

https://www.sqlbi.com/articles/understanding-how-dax-evaluates-if-statements/

New version of DAX Studio (3.3.0) has nice new features!
"Run a query on a PBIX file that is not open," and now DSCMD (command-line version) opens it for you!
There are 41 other items in the release note.
Immediate upgrade!

https://daxstudio.org/blog/v3_3_0-release/

#powerbi #dax #daxstudio

This article + video describes how to control the execution of DAX code when there are either multiple or empty selections of calculation items in calculation groups.

#powerbi #dax #calculationgroups

https://www.sqlbi.com/articles/controlling-empty-or-multiple-selections-in-calculation-groups/

This article + video explains the error "Can't determine relationship between the fields" when placing columns from unrelated tables in a Power BI matrix.

#powerbi #matrix #dax

https://www.sqlbi.com/articles/understanding-the-cant-determine-relationship-between-the-fields-error-in-power-bi/

The “Choosing Between Import Mode, Direct Lake, and Composite Models” session is available!
The new "Direct Lake + Import" composite model feature is in public preview.

https://www.sqlbi.com/blog/marco/2025/05/13/direct-lake-vs-import-vs-direct-lakeimport-fabric-semantic-models-may-2025/

This article + video overviews some tools available to create semantic models and reports in Power BI.

Make your life easier!

#powerbi #tools #dax

https://www.sqlbi.com/articles/tools-in-power-bi/