Microsoft Power BI is one of the leading business intelligence platforms available today. For four consecutive years, Power BI has been positioned furthest in 'completeness of vision' and highest in 'ability to execute' on the Gartner Magic Quadrant for BI platforms.
Power BI's success and popularity mean a high demand for strong Power BI talent in the marketplace. To learn all that is possible if you master Power BI, read our post on what you can do with Power BI.
However, this popularity also means that it can be a very competitive job market to get into. If you want to land a job requiring a Power BI specialty, then the best way to set yourself up for success is to prepare for the interview. If you're invited to an interview, you can be sure your application made a good impression.
The most important thing you can do to ensure you successfully land the job is to prepare for the interview. Depending on the nature of the job, your future employer will likely ask highly technical questions relating to Power BI. Employers want to assess how well you know how to use the platform. This blog post will take you through some of the most common categories, elements, and questions you can expect in a Power BI job interview.
You can even approach your Power BI job search in true data analyst fashion by using your skills to analyze job market data. Our course on analyzing job market data will walk you through the entire process!
Power BI Basic Interview Questions
For entry-level or junior Power BI jobs, you need to be able to talk about some basic Power BI concepts. You should understand the purpose of Power BI in an organization, how it can best bring them value, and some potential risks or downsides to be aware of when using the platform. You should also be very familiar with how to use Power BI Desktop and the Power BI Service. To learn data analysis with Power BI, see our Data Analyst in Power BI career track.
Let's go through each of these basic Power BI interview questions.
Interview Questions on The Function and Purpose of Power BI
These types of interview questions test your knowledge of the importance and usefulness of BI platforms. You must be able to demonstrate that you understand the value of BI in an organization.
What are the benefits of self-service BI platforms like Power BI?
Self-service BI emphasizes the user rather than the developer. It empowers the user to find solutions and generate insights independently without waiting for another dedicated department (like IT) to do it for them.
Do you know of other BI platforms? How does Power BI compare to them?
Another top-rated BI platform is Tableau, which is an excellent alternative to Power BI. However, one of the most significant advantages of using Power BI over Tableau is that there is usually a much lower learning curve for Power BI. This is especially true if the developer (or the user) is already familiar with Microsoft Excel since Power BI uses many of the same elements as in Excel.
See our standalone article for a full breakdown of Power BI vs Tableau.
What are some of the disadvantages or risks that we should look out for as we use Power BI?
One of the biggest disadvantages of using Power BI is that their cloud-based solution (Power BI Service) is locked into the Microsoft ecosystem. Only those with a Microsoft 365 account and Power BI PRO subscription can access reports and dashboards. In addition, another disadvantage is that Power BI desktop only works on Windows and cannot be installed on machines that run MacOS or Linux.
Power BI Desktop & Power BI Service Interview Questions
What is Power Query, and what is it used for in Power BI?
Power Query is an ETL (Extract, Transform, Load) tool within Power BI. It allows us to import, clean, transform, merge, and modify data sets.
What are the different types of filters in Power BI reports?
Power BI reports can be filtered using slicer visuals or through the collapsable filter pane on the right-hand side of Power BI. Slicer visuals are intuitive and easy to use. The filter pane offers more complex filtering options, such as page-level, report-level, and drillthrough filters. However, this can stay hidden from the user and be preset and locked so that they persist for all users.
What's the difference between a report and a dashboard in Power BI?
Power BI reports are typically designed using Power BI desktop and are then published to the Power BI service. On the other hand, dashboards are made up of 'tiles' from one or more reports in a single workspace. Dashboards allow us to condense present insights from multiple reports in one place.
How can we refresh the data in a report published to Power BI Service?
Data that is imported from an on-premise storage location can only be refreshed from Power BI service through a gateway. This offers a secure way for cloud-based reports to access locally-stored data.
Power BI DAX Interview Questions
Most Power BI job interviews will include questions about DAX - they are a critical component of Power BI. You should understand DAX functions and how to construct them in detail. From basic functions like SUM and COUNT to more complex functions like RANKX.
Additionally, you should be familiar with how these expressions interact with each other, knowing how to prevent circular dependencies and optimize your DAX expressions to ensure high-performing reports. Lastly, you should also be able to debug your DAX formulas, finding and fixing errors or typos. We will break down each of these aspects of DAX in this section.
Understanding DAX Functions and Expressions
What is the difference between DAX functions, expressions, and variables?
- DAX functions are pre-built definitions that allow you to perform calculations on your data.
- DAX expressions are made up of one or more DAX functions.
- Variables store the results of a DAX expression for use within a particular DAX expression.
What's the difference between a measure and a calculated column in Power BI?
Measures and calculated columns both use DAX expressions. However, measures perform an aggregation on the data and will return a value based on the filters in the report. Calculated columns return the result of a DAX expression for each row of a table. The result of a calculated column can be viewed just like any other column in the Data and Model views.
Describe how you would use function X
The types of functions that are asked about in this question are unique for each organization. However, you should have a good understanding of most of the available DAX functions in Power BI.
What are circular dependencies? How can you avoid creating circular dependencies in your DAX expressions?
Circular dependencies are created when two expressions reference each other, and Power BI doesn't know which one to calculate first to determine the result. Usually, circular dependencies occur when improperly using the CALCULATE function.
Power BI Technical Interview Questions
Intermediate to senior-level Power BI jobs that require at least a few years of experience will usually involve technical questions around architecture, connectivity, and data modeling in Power BI. You should be familiar with the components that make up BI solution architecture in general and how Power BI fits into this architecture.
You should also know how to connect Power BI to multiple data sources and import and transform that data in Power BI (using Power Query). Additionally, it would be best if you had a good understanding of data modeling principles and the best practices for them. Lastly, the technical interview may also involve questions about data refresh and the Power BI gateway for the deployment of reports to the cloud using Power BI Service.
Power BI Architecture
In this section, you could be asked about BI solution architecture at a high-level and/or about one or more elements within the solution architecture framework. Here, it is good to understand BI solution architecture in general and how Power BI fits into each element. So let's go over them briefly.
BI semantic models are built using BI platforms like Power BI. They are usually built on top of existing structured data models, like in a data warehouse or database. After that, these reports can be published to a cloud platform to share with business users, as is the case when publishing to Power BI Service.
One of Power BI's most important (and powerful) aspects is data modeling. Some of these concepts can be highly complex, so take your time to understand them well.
Describe what a star schema is and how it works.
A star schema is made up of a central fact table and multiple dimension tables branching off this fact table, giving the appearance of a star. A fact table is made up of values that can be aggregated, as well as one or more keys that link to the dimension tables.
What is cardinality?
Four cardinality choices exist: many-to-one, one-to-one, one-to-many, or many-to-many. When creating relationships, it is recommended that the joining field contains unique values in at least one of the tables. This allows you to use the one-to-many or many-to-one options in your data model.
Explain the difference between single and bi-directional relationships
The directionality of relationships is defined using the cross-filter direction option. Relationships flow from the table with unique values to the table with many values, affecting filtering. The single direction is recommended for most cases.
Describe a common issue with using many-to-many cardinality in a relationship
Many-to-many relationships can become an issue if there are different levels of granularity in the data. Power BI cannot infer greater levels of granularity if it does not exist in one of the tables. This causes the results of calculations to get duplicated according to the filter applied.
Interview Questions on Data Gateways for Power BI Service
If the organization you are interviewing with uses on-premise data stores, then they will likely use data gateways. These are some of the more tricky questions you can encounter on gateways.
What's the difference between a standard and a personal gateway?
The personal gateway is linked to the user account that installed it. This means that multiple users cannot share and configure the gateway. For example, if the user left the organization and their user account was deleted, the gateway would stop working. On the other hand, a standard gateway is not linked to any user account and allows more centralized management of data sources. In addition, the standard gateway supports other connection types, such as Direct Query.
What considerations should be made when choosing a machine to install the gateway on?
The biggest factor affecting the performance of data gateways is the number of concurrent users consuming the report. This is especially important to consider if any reports use real-time data connections.
Can a gateway contain both import and direct query connections?
Yes. However, using separate gateways for import and direct query connections is good practice. This is because direct query connections can place a lot of strain on the machine that the gateway is installed on. To avoid delays or potential issues as you scale the number of reports and the number of users for those reports, it is best to use separate gateways.
Power BI Scenario-Based Interview Questions
For intermediate-level Power BI jobs and above, it is common to receive scenario-based interview questions. These questions are unique to the company you are interviewing for and depend on their industry and how Power BI is used in their organization. However, there are some common themes between these scenario-based questions, and they can be used to test your knowledge of some Power BI concepts.
For a complete walkthrough of a case study for a job interview, see this live training session on Solving a Job Interview Case Study with Power BI.
Handling Complex & Large Data Sets
We want to design a Power BI report on complaints and compliments received through our customer services department. However, this information is located within a folder of about 100 files. How would you go about importing these files into Power BI?
You can select an entire folder as a data source in Power BI. Using the format from a single file in the folder, you can import all files according to that same format. However, it is essential to remember that every file should follow the same format, or the imported data will make little sense.
We currently have a Power BI report that imports a large volume of data from our warehouse. How would you optimize the performance of a Power BI report for big data?
There are three basic things you can do to immediately improve the performance of reports that use large volumes of data:
- Turn off time intelligence - this is a feature of Power BI that automatically creates date/time hierarchies every time a date field is added to a visual, causing a bloated, slow Power BI report.
- Only load the columns you actually need - if a column is not used in the report, do not import (for example, ID fields).
- Only load the rows you actually need - it is better to either filter out or aggregate historical data.
Advanced Power BI Interview Questions
Most senior-level Power BI jobs will try to test very advanced Power BI concepts in their job interviews. You may get some scenario-based questions, as in the above section, along with some of the advanced questions in this section.
You should prepare to answer questions about how to approach complex data modeling problems with potentially large data sets and how to effectively design the Power BI reports for these problems.
Lastly, this section may also include questions about Power BI's advanced analytics and AI capabilities. You should be familiar with the latest developments and releases of Power BI so that you know what Power BI is capable of and what can best be used to benefit the company.
Advanced-Data Modeling & Design Techniques
The questions in this section typically focus on optimization techniques as they apply to data modeling and design. For example:
- What workarounds exist to avoid using bi-directional filters in relationships? One way to do this is to include additional visual-level filters for the visuals that rely on a single directional filter.
- Explain how you would design a report for optimal and intuitive navigation. The key to optimal navigation in Power BI reports is to use bookmarks and buttons. Additionally, good use of icons in the report can save space and make navigation more intuitive.
Advanced Analytics & AI
These features of Power BI can significantly improve the speed and quality of insights you generate from reports. You should be familiar with these as well as any new features:
- What-if parameters in Power BI visuals
- Anomaly detection
- Key influencers visual
- Decomposition trees
- Smart narratives
- Context-specific insights
Power BI Interview Questions for Experienced Professionals
The final section of this blog post is reserved for experienced Power BI professionals. When interviewing for very high-level Power BI jobs in an organization, you will typically not get asked about any of the technical aspects of Power BI. Instead, the interview will focus on your past experiences and knowledge of report optimization, governance, and management. At this level, you should be familiar with working with or leading Power BI teams, choosing the best approach or solution for a business problem, and implementing it from working with stakeholders on problem definition to deployment and maintaining and improving those projects over time.
Discussing a Challenging Power BI Project
This will be unique to your own experiences. However, you can prepare for this type of question by thinking about your previous projects with these guidelines:
- What was the business problem and associated solution using Power BI?
- What approach did you take when applying Power BI?
- What challenges did you encounter, and how did you address those challenges?
Data Governance & Security
Data governance is a highly complex topic, generally reserved for experienced Power BI professionals. You should know the regulations and policies that make up a good governance strategy. This involves aspects such as:
- Policies around user permissions and access.
- Policies and decision guidelines around workspaces, gateways, sharing, administration, privacy, data sources, etc.
- Policies for satisfying the conditions for any regulations in your industry and/or country.
- Understanding and reducing the risk of data leakage.
Some of the most essential Power BI interview questions are highly technical - such as those on DAX and data modeling. To land a job and make a great first impression in an interview, it is crucial to go into it well-prepared.
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Maarten Van den Broeck