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.

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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”

Power BI Governance, What Organisations Need to Know

Power BI Governance Art Built by Bing Image Creator

In recent years, Power BI has become one of the most widely used business intelligence (BI) tools. Power BI is more than just a reporting tool; it is a comprehensive analytical platform that enables users to collaborate on data insights and share them internally and externally. In addition to creating reports and dashboards, Power BI allows users to collaborate and share their work with others. For instance, users can share dashboards with their colleagues, allowing them to view, interact, and engage with the data quickly. However, as more organisations adopt Power BI, it becomes essential to ensure appropriate governance processes, policies, and rules are in place. This blog post explains Power BI governance and why business owners need to be conscious of it.

Power BI governance refers to a set of processes, policies, and standards that organisations put in place to manage and control the use of Power BI. Governance is critical to ensure that the use of Power BI is aligned with the organisation’s objectives and strategy, complies with relevant regulations and standards, and protects sensitive data. Power BI governance encompasses several areas, including security, data management, compliance, and user management. It also involves defining data access, sharing, security, and compliance guidelines within Power BI. This includes defining roles and permissions for users, specifying approved data sources that can be used, and ensuring that the data is accurate, up-to-date, and secure across the organisation. In addition, Power BI governance involves monitoring and auditing the use of Power BI to ensure that it is being used appropriately and in compliance with the organisation’s policies. Lack of Power BI governance can impact businesses in various negative ways, so it is important that everyone within the organisation, especially the managerial teams, has a good understanding of how they can benefit from supporting the establishment of Power BI governance across the organisation. Here are some reasons:

  • Better decision-making
    With Power BI governance in place, organisations can ensure that the data used in decision-making is accurate, consistent, and trustworthy. This can help them make informed decisions based on reliable data insights.
  • Improved security and compliance
    Power BI governance helps to establish security measures to protect sensitive data and ensure compliance with regulations and industry standards. This helps to avoid costly data breaches and non-compliance penalties.
  • Efficient use of resources
    By establishing guidelines for roles and responsibilities, data access, sharing, and storage, Power BI governance can help organisations use their resources more efficiently. This can result in cost savings and improved productivity.
  • Enhanced collaboration
    Having Power BI governance policies help business owners to promote collaboration and communication among team members. This can result in improved teamwork and better outcomes for the organisation.
  • Better management and control
    Power BI governance helps organisations to manage and control the use of Power BI within the organisation. This can help them ensure that the tool is being used effectively and efficiently and that data is being used in a way that aligns with their business objectives.
Continue reading “Power BI Governance, What Organisations Need to Know”

Power BI 101, What Should I Learn?

This is the second part of my new series of Power BI posts named Power BI 101. In the previous post, I briefly discussed what Power BI is. In this post, I look into one of the most confusing parts for those who want to start learning Power BI. Many people jump straight online and look for Power BI training courses which there are plenty out there. But which one is the right training course for you? Let’s find out.

What do you want to gain from learning Power BI?

Regardless of attending paid training courses or being a self-learner, the above question is one of the most important questions you might ask yourself before going to the next steps. The answer to this question dictates the sort of training you must look for. Your answer to the preceding question can be one or none of the following:

  • I am a graduate/student looking at the job market
  • I am a business analyst and I want to know how Power BI can help you with my daily job
  • I am a database developer and I want to learn more about business intelligence and data and analytics space
  • I am a non-Microsoft Business Intelligence developer and I want to start learning more about Microsoft offerings
  • I am a system admin and I have to manage our Power BI tenant
  • I am a data scientist and I want to know how I can use Power BI
  • I am just ciourious to see what Power BI can do for me

As mentioned, your answer might not be any of the above, but, thinking about your reason(s) for learning Power BI can help you to find the best way to learn and use Power BI more efficiently. You can spend time and money taking some online courses and get even more confused. You don’t want that do you?

So, whatever reason(s) you have in mind to learn Power BI, most probably you fall into one of the following user categories:

Think about your goal(s) and what you want to achieve by learning Power BI then try to identify your user category. For instance, if you are a student thinking of joining an IT company as a data and analytics developer, then your user category is most probably a Power BI Developer or a Contributor.

To help you find out your user category let’s see what the above user categories mean.

Power BI Developers

The Power BI Developers are the beating hearts of any Power BI development project. Regardless of the project you will be involved with, you definitely require to have a certain level of knowledge of the following:

  • Data preparation/ETL processes
  • Data warehousing
  • Data modelling/Star schema
  • Data visualisation

To be a successful Power BI developer you must learn the following languages in Power BI:

  • Power Query
  • DAX

Depending on the types of projects you will be involved in, you may require to learn the following languages as well:

  • Microsoft Visual Basic (for Paginated Reports)
  • Python
  • R
  • T-SQL
  • PL/SQL

As a Power BI developer, you will write a lot of Power Query and DAX expressions. Most probably you require to learn T-SQL as well. The following resources can be pretty helpful:

Continue reading “Power BI 101, What Should I Learn?”

Introducing Power BI Governance and Adoption Good Practices Series

Introducing Power BI Governance Series

In my experience working in IT industry from early 2000 one aspect of dealing with data that is always taken very seriously is data governance.

For many years the industry learnt how important it is to have a data governance process in place to keep your data safe and healthy so you get the most out of your data. Power BI is no different to any other data platforms, so data governance is an important part of it. However, the concept of self-service data management which offers all the beauties and power an agile approach caused some organisations not to think about their governance approach from the outset.

On the other hand, some people find governance as a burden which slows down the adoption. Some people think even worse, they think governance is a stopper which puts a lot of unnecessary restrictions in place which decreases efficiency.

But in reality if you start data governance planning sooner than later you can protect your organisation from a lot of risks down the road which can get really nasty and costly like:

  • Risk of law suits due to data leakage and privacy issues
  • Untrusted data analysis and reporting due to poor quality of data
  • Poor performing solution due to lack of auditing
  • Inefficient development outcomes due to undefined environments
Risks of lack of governance
Continue reading “Introducing Power BI Governance and Adoption Good Practices Series”