Skip to main content
cancel
Showing results for 
Search instead for 
Did you mean: 

Join us for an expert-led overview of the tools and concepts you'll need to become a Certified Power BI Data Analyst and pass exam PL-300. Register now.

Reply
Walt1010
Helper IV
Helper IV

How/where is the M language read loop?

I realise that what Im remarking on is probably a beginners viewpoint, but when I look at a M language query, and compare it to a typical language like Python or C , I struggle to understand the flow of control when it comes to process rows of data, or file records. The "input" section is intuitive but where the "loop" is that circles back and reads the next row, isn't explicit. Am I correct?

1 ACCEPTED SOLUTION
Anonymous
Not applicable

Hi @Walt1010 ,

 

In M, the concept of looping through rows is abstracted away. Instead, M uses functions and transformations to process data. For example, when you apply a transformation to a table, M applies that transformation to each row without explicitly showing a loop. This can make it seem like there is no control flow, but in reality, M handles it behind the scenes.

 

In below example, we start by loading the sample data into a table. Then, we add a new column called "Total Sales" that calculates the total sales for each row by multiplying the "Sales" column by 1.1. Notice that there are no explicit loops; the Table.AddColumn function applies the transformation to each row automatically. This is a simple demonstration of how M processes data in a functional and declarative manner.

vkongfanfmsft_0-1734077681937.png

vkongfanfmsft_1-1734077701722.png

 

Best Regards,
Adamk Kong

 

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

View solution in original post

2 REPLIES 2
Anonymous
Not applicable

Hi @Walt1010 ,

 

In M, the concept of looping through rows is abstracted away. Instead, M uses functions and transformations to process data. For example, when you apply a transformation to a table, M applies that transformation to each row without explicitly showing a loop. This can make it seem like there is no control flow, but in reality, M handles it behind the scenes.

 

In below example, we start by loading the sample data into a table. Then, we add a new column called "Total Sales" that calculates the total sales for each row by multiplying the "Sales" column by 1.1. Notice that there are no explicit loops; the Table.AddColumn function applies the transformation to each row automatically. This is a simple demonstration of how M processes data in a functional and declarative manner.

vkongfanfmsft_0-1734077681937.png

vkongfanfmsft_1-1734077701722.png

 

Best Regards,
Adamk Kong

 

If this post helps, then please consider Accept it as the solution to help the other members find it more quickly.

Greg_Deckler
Super User
Super User

@Walt1010 You don't really have classic while and for loops in M. You have recursion and you have things like List.Generate where you can emulate their behavior more or less. It's the same story for DAX, no traditional while or for loops but you can emulate their behavior.



Follow on LinkedIn
@ me in replies or I'll lose your thread!!!
Instead of a Kudo, please vote for this idea
Become an expert!: Enterprise DNA
External Tools: MSHGQM
YouTube Channel!: Microsoft Hates Greg
Latest book!:
Power BI Cookbook Third Edition (Color)

DAX is easy, CALCULATE makes DAX hard...

Helpful resources

Announcements
Join our Fabric User Panel

Join our Fabric User Panel

This is your chance to engage directly with the engineering team behind Fabric and Power BI. Share your experiences and shape the future.

June 2025 Power BI Update Carousel

Power BI Monthly Update - June 2025

Check out the June 2025 Power BI update to learn about new features.

June 2025 community update carousel

Fabric Community Update - June 2025

Find out what's new and trending in the Fabric community.