Understanding Power BI Totals: The Math, the Model, and the Misconceptions

The long-running debate around how Power BI calculates totals in tables and matrices has been part of the community conversation for years. Greg Deckler has kept the topic alive through his ongoing “broken totals” posts on social media, often suggesting that Power BI should include a simple toggle to make totals behave more like Excel. His continued campaign prompted a detailed reply from Daniel Otykier in his article No More Measure Totals Shenanigans, and earlier, Diego Scalioni explored how DAX evaluates totals internally in his post Cache me if you can: DAX Totals behind the scenes.

This blog brings all those perspectives together from a scientific and comparative angle. It looks at how totals are calculated in Power BI and compares that behaviour with Tableau, Excel, Paginated Reports, QlikView and even T-SQL. The goal is not to take sides, but to clear up the confusion around what is happening under the hood.

If you are into podcasts and prefer the audio version of this blog, I got you covered. Here an AI generated podcast for this blog. 👇

Power BI’s Broken Totals – Myth Debunked

Are Power BI Totals Really Broken?

Let’s get one thing clear right at the start, no, Power BI totals are not broken. There is no “it depends” this time. What some interpret as broken behaviour is actually how DAX and the underlying model are designed to work.

This post is not personal, it is purely scientific and technical. While I have great respect for Greg and his significant contributions to the Power BI community, I disagree with the use of the word “BROKEN.” It sounds dramatic but does not reflect the full truth. Totals in Power BI behave exactly as the model and the maths define them to. Want to know why? Keep reading.

Why this matters

When someone with Greg’s influence keeps saying totals are “broken”, it really affects how new users see Power BI. Some even start thinking the tool itself is not reliable, when what they are seeing is actually how different reporting tools do their calculations in different ways.

It helps to know the main calculation styles that these tools use:

  • Cell based: This is what you get in worksheet formulas and classic PivotTables that use Excel ranges. Totals are just simple sums of the shown items, with no model or relationships behind the scene.
  • Model driven: This is how Power BI works and also Excel PivotTables that use the Data Model (Power Pivot) or connect to a tabular dataset. Measures are calculated again for every context, so totals depend on how filters and relationships are set.
  • Query driven: Tools like Paginated Reports work this way. The report runs a query, for example SQL or DAX, gets the dataset, and then sums or averages values in the report design. The author decides how each total should be calculated.
  • Hybrid (query and context driven): Tableau fits in here. It gets the data through a query but also lets you change the level of detail and how totals behave in the visual. So sometimes it acts like a query tool and sometimes more like a model one.

Most of the confusion happens when people compare results from these tools as if they all worked the same way. Once you understand the difference between cell based, model driven, query driven, and hybrid tools, the way Power BI shows its totals starts to make full sense.

The problem that started it

Greg’s long-running example uses a small table with a single column of numbers and a DAX measure like this:

SUMX(SampleData, SampleData[Amount]) - 10

In the total row, the result shows 590, while he expects 580 (two groups of 290 each). Based on that, he argues that Power BI totals are “wrong”.

But DAX is only doing what it is told to do. In this measure, the subtraction of 10 happens after the total amount is calculated, not for each row. If the intention was to take 10 away per row, then the measure should be written like this:

SUMX(SampleData, SampleData[Amount] - 10)

This version gives the expected 580 because the subtraction now happens at the lowest level of detail, which is per row.

This might look like a small detail, but it is exactly where most of the confusion around totals begins. The difference is not about Power BI being wrong; it is about understanding where in the calculation the operation happens.

The math behind it

Before we look at the numbers, let’s first talk about what we are trying to do. We Greg’s small and very simple table that shows some amounts by Category and Colour:

CategoryColourAmount
ARed100
AGreen100
ABlue100
BRed100
BGreen100
BBlue100
Continue reading “Understanding Power BI Totals: The Math, the Model, and the Misconceptions”

Quick Tips: Time Dimension with Time Bands at Seconds Granularity in Power BI and SSAS Tabular

Time Dimension with Time Bands at Seconds Granularity in Power BI and SSAS Tabular

I wrote some other posts on this topic in the past, you can find them here and here. In the first post I explain how to create “Time” dimension with time bands at minutes granularity. Then one of my customers required the “Time” dimension at seconds granularity which encouraged me to write the second blogpost. In the second blogpost though I didn’t do time bands, so here I am, writing the third post which is a variation of the second post supporting time bands of 5 min, 15 min, 30 min, 45 min and 60 min while the grain of the “Time” dimension is down to second. in this quick post I jump directly to the point and show you how to generate the “Time” dimension in three different ways, using T-SQL in SQL Server, using Power Query (M) and DAX. Here it is then:

Time Dimension at Second Grain with Power Query (M) Supporting Time Bands:

Copy/paste the code below in Query Editor’s Advanced Editor to generate Time dimension in Power Query:

let
Source = Table.FromList({1..86400}, Splitter.SplitByNothing()),
#"Renamed Columns" = Table.RenameColumns(Source,{{"Column1", "ID"}}),
#"Time Column Added" = Table.AddColumn(#"Renamed Columns", "Time", each Time.From(#datetime(1970,1,1,0,0,0) + #duration(0,0,0,[ID])), Time.Type),
    #"Hour Added" = Table.AddColumn(#"Time Column Added", "Hour", each Time.Hour([Time]), Int64.Type),
    #"Minute Added" = Table.AddColumn(#"Hour Added", "Minute", each Time.Minute([Time]), Int64.Type),
    #"5 Min Band Added" = Table.AddColumn(#"Minute Added", "5 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/5) * 5) + 5, 0)), Time.Type),
    #"15 Min Band Added" = Table.AddColumn(#"5 Min Band Added", "15 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/15) * 15) + 15, 0)), Time.Type),
#"30 Min Band Added" = Table.AddColumn(#"15 Min Band Added", "30 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/30) * 30) + 30, 0)), Time.Type),
#"45 Min Band Added" = Table.AddColumn(#"30 Min Band Added", "45 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/45) * 45) + 45, 0)), Time.Type),
#"60 Min Band Added" = Table.AddColumn(#"45 Min Band Added", "60 Min Band", each Time.From(#datetime(1970,1,1,Time.Hour([Time]),0,0) + #duration(0, 0, (Number.RoundDown(Time.Minute([Time])/60) * 60) + 60, 0)), Time.Type),
    #"Removed Other Columns" = Table.SelectColumns(#"60 Min Band Added",{"Time", "Hour", "Minute", "5 Min Band", "15 Min Band", "30 Min Band", "45 Min Band", "60 Min Band"})
in
    #"Removed Other Columns"
Continue reading “Quick Tips: Time Dimension with Time Bands at Seconds Granularity in Power BI and SSAS Tabular”

Quick Tips: Keyboard Shortcuts/Hotkeys When Writing DAX in Power BI Desktop

DAX Keyboard Shortcuts in Power BI Desktop

Keyboard shortcuts is an interesting topic for developes that can really improve your report development in Power BI Desktop. In this post I show you some keyboard shortcuts/hotkeys when writing DAX in Power BI Desktop.

 

  • Indend right: Ctrl + ]
  • Indent left: Ctrl + [

Mini-tip: You can also indent your code to ther right by pressing TAB or indent left by pressing Shift + TAB. But, the difference is that if your cursor is in the middle of a line, when you press TAB it divides your code to two pieces and indends the characters to the right from the position that cursor is in.

  • New line keep indent: Shift + Enter
  • New line starting from first of line: Alt + Enter
  • Activate Intellicence: Ctrl + Space
  • Comment multiple lines: Ctrl + KC or Ctrl + /
  • Uncomment multiple lines: Ctrl + KU or Ctrl + /
  • Move the current line up/down: Alt + Up/Down Arrow Key
  • Enter multiple lines of code at once: Ctrl + Alt + Up/Down Arrow Key
  • Find and replace a word: Ctrl + D to highlight the current word, Ctrl + D again to find/highligh the same next word. Continue pressing Ctrl + D to find/highlight all same words, then start typing to replace all words at once
  • Find and replace all of a kind at once: Ctrl + Shift + L to highlight a part of your DAX expression then start typing to replace the highlighted words at once

Continue reading “Quick Tips: Keyboard Shortcuts/Hotkeys When Writing DAX in Power BI Desktop”

Creating Custom Table in SSAS Tabular using Table and Row Constructors in DAX

Dynamic_Measures_in_Card_Visual_-_Power_BI_Desktop

A while ago I was working on a Power BI project which the customer wanted to define a new table directly in the model. The easiest way to achieve this in Power BI Desktop is to “Enter Data” which creates a new table by typing or pasting in new contents. I was thinking of that project the other day and thought, hey, how we can do the same in SSAS Tabular when there is no Power Query (M) language available in SSAS Tabular 2016. The good news is that Power Query will be available in the next version of SSAS Tabular in SQL Server vNext. But, until then a workaround would be entering data to a CSV file then load it to the model. Another way is to implement custom tables in DAX in SQL Server 2016 Tabular models using Table and Row Constructors. In this post I show you a way of creating custom table in SSAS Tabular using table constructors in DAX. You can do the same in Power BI as the same principle applies. Therefore, in case you’d prefer not to use “Enter Data” feature which effectively uses Power Query to create a new table in Power BI Desktop, then you can use DAX to do the same.

Requirements

If don’t already have SQL Server 2016 it’s probably time to download and install it. I use AdventureWorksDW as sample database in this article.

Scenario

You are involved with an SSAS Tabular project and the customer asked for a report in Power BI with dynamic Card so that the values shown in the Card visual should dynamically change based on selected measure from a slicer. You have several different measures in the model and the customer wants to show some of them dynamically in only one Card visual. Consider you have the following measures to be shown in the Card:

  • Total Internet Sales
  • Internet Sales in 2014
  • Total Number of Internet Sales Transactions

You have to create a logic so that the users can selected any of the above measures to show in a single Card visual.

How it works

After you meet the requirements, you’re good to start implementing the above scenario in SQL Server Data Tool (SSDT). Creating a calculated table in SSAS Tabular 2016 is fairly easy. All we need to do is to create a custom table with two columns. One column stores friendly names for measures and the other one holds DAX expressions for the measures. As you might have noticed, I’m talking about creating a custom table in DAX and populating it with values. Continue reading to see how. What we are going to do is to create a calculated table using table constructors in DAX. Table and Row Constructors weren’t available in previous versions of DAX in SSAS Tabular. They are very similar to Lists or a list of Tuples just like what we have in MDX.

I’ll explain this later when we created our sample model in SSDT.

Continue reading “Creating Custom Table in SSAS Tabular using Table and Row Constructors in DAX”