π Data modeling
π Power Query
π Relationships & RLS
⚖️ Measures vs Calculated Columns
π Performance optimization
π§ Real-world project scenarios
Tell me about yourself
Answer – I’m a data analyst with strong expertise in Power BI, DAX, Power Query, and data modeling. I’ve worked on multiple end-to-end BI projects, transforming raw data into meaningful dashboards and KPIs. My focus is on driving insights, improving data accessibility, and enabling data-driven decisions.
Difference between Calculated Columns and Measures
Answer – Calculated Columns are row-based and stored in the data model, increasing file size. Measures are calculated on-the-fly based on context, are more efficient, and don’t increase model size.
How to handle missing values?
Answer – Use Power Query to identify and treat nulls. Techniques include replacing nulls, removing incomplete rows, or filling them based on business rules.
Difference between SUM and SUMX
Answer – SUM totals a single column directly. SUMX evaluates an expression row by row over a table and then sums the results.
What is DAX? Give an example and mention the DAX functions used in your project
Answer – DAX (Data Analysis Expressions) is a formula language in Power BI.
Example: CALCULATE(SUM(Sales[Revenue]), Region[Name] = “West”)
In my projects, I’ve used functions like CALCULATE, FILTER, ALL, and time intelligence functions such as SAMEPERIODLASTYEAR and TOTALYTD.
How do you disable a graph that is changing dynamically?
Answer – Use Edit Interactions to control how visuals affect each other. Disable the interaction for that specific graph to stop it from being filtered by others.
Explain RLS (Row-Level Security) and how to implement it
Answer – RLS restricts data access for users based on roles. It is implemented via Manage Roles in Power BI Desktop using DAX filters like Region[Region] = USERPRINCIPALNAME().
Types of filters in Power BI
Answer –
Report-level
Page-level
Visual-level
Drillthrough
Slicers
Cross-filtering
Difference between Drill Down and Drill Through
Answer – Drill Down lets you explore data hierarchies within the same visual. Drill Through takes you to a different report page filtered by selected data.
Explain the process of publishing the report
Answer – Save the report in Power BI Desktop, click “Publish,” and select the target workspace in Power BI Service. Then, configure data refresh schedules and manage access permissions.
How to create relationships in Power BI? Types of Cardinality?
Answer – Use Manage Relationships to define relationships between tables.
Types of cardinality: One-to-One, One-to-Many (most common), and Many-to-Many.
How to schedule refresh in Power BI?
Answer – In Power BI Service, go to Dataset > Settings > Schedule Refresh. Set frequency, time, and credentials. Use a gateway for on-premise data sources.
What type of account did you use and what are its features?
Answer – I used a Power BI Pro account. It allows report sharing, content publishing, scheduled refreshes, collaboration within workspaces, and RLS implementation.
How to perform join operations in Power BI?
Answer – Use Merge Queries in Power Query. Join types include Inner, Left Outer, Right Outer, Full Outer, and Anti Joins.
What are good practices in Power BI?
Answer –
Use a star schema
Limit calculated columns
Use meaningful naming conventions
Simplify visuals
Use variables in DAX
Optimize performance with Performance Analyzer
Disable Auto Date/Time for better model size
Explain your latest Power BI project
Answer – I developed a sales dashboard for a retail company. I used SQL Server as a source, Power Query for cleaning, and modeled data using a star schema. I created KPIs like total sales, profit margin, and YoY growth, and implemented RLS for different regional users.
Difference between Slicer and Filter
Answer – A slicer is a visual element that users interact with to filter data on the report. Filters are applied in the filter pane and can be set at the visual, page, or report level without being visible to end users.
Top 10 Scenario-Based Power BI Interview Questions & Answers
How to optimize a Power BI report for performance?
Answer – Use proper data modeling (star schema over snowflake).
Reduce the number of visuals on each page.
Avoid using too many slicers or filters.
Replace calculated columns with measures where possible.
Use variables in DAX to avoid repetitive calculations.
Disable Auto Date/Time.
Limit the data loaded using query filters.
Use Performance Analyzer to find and fix slow visuals.
How do you optimize a Power BI report that takes a long time to load?
Answer – Identify heavy visuals using Performance Analyzer.
Remove unnecessary columns from the data model.
Use aggregations and summary tables.
Avoid complex DAX calculations in visuals.
Split large reports into multiple pages or files.
Ensure relationships are properly indexed.
How to deal with Power BI report refresh issues?
Answer – Check data source connectivity and gateway configuration.
Verify credentials and permissions.
Reduce data size or filter out unnecessary rows during load.
Break large queries into smaller steps in Power Query.
Monitor refresh logs in Power BI Service to identify bottlenecks.
How do you integrate Power BI with various data sources?
Answer – Use built-in connectors for sources like SQL, Excel, SharePoint, Salesforce, etc.
For unsupported sources, use OData, Web API, or custom connectors.
Use gateways to connect to on-premise data.
Schedule refreshes for regularly updating sources.
You have multiple regional sales teams and each team should access only their data. How do you manage this?
Answer – Implement Row-Level Security (RLS).
Create a user-region mapping table.
Use DAX filter like Region[Name] = LOOKUPVALUE(UserRegion[Region], UserRegion[User], USERPRINCIPALNAME()).
Assign roles and test them in Power BI Desktop and Service.
Users report incorrect data in reports. How do you approach this?
Answer –Reproduce the issue based on user feedback.
Check the data source for inconsistencies.
Validate the DAX logic and transformations in Power Query.
Use filters or bookmarks to test different contexts.
Communicate findings and apply corrections with proper documentation.
Your team is working on multiple reports using redundant tables. How do you manage this?
Answer – Centralize shared tables in a common dataset.
Use Power BI’s shared dataset feature.
Promote and certify datasets to avoid duplicates.
Encourage modular report development.
How do you train your team to write proper DAX queries?
Answer –
Conduct regular DAX workshops and code reviews.
Share reusable DAX patterns and best practices.
Use Microsoft’s DAX Guide and official documentation.
Encourage using variables, comments, and formatting in DAX for readability.
How do you handle a data transformation project from scratch?
Answer – Understand business requirements and define KPIs.
Identify and connect to data sources.
Use Power Query to clean, transform, and shape the data.
Build a logical data model with proper relationships.
Develop reports and visuals based on user roles.
Test and deploy with feedback loops.
How do you implement a near real-time reporting solution?
Answer – Use DirectQuery or hybrid models for real-time data access.
Ensure source systems support high availability and fast querying.
Optimize visuals and minimize data transformations.
Use streaming datasets for real-time dashboards.
Top 5 Power BI Interview Questions & Answers
Suppose scheduled refresh took 10 minutes yesterday and 30 minutes today. All credentials and settings are fine — what could be the reason?
Answer – Data volume may have increased significantly.
Source system performance may have been slower.
Query complexity or transformations might have changed.
Network latency or server load in Power BI Service may have varied.
A gateway performance issue or increased concurrent refreshes could also be a factor.
Your PBIX file is not getting published — what are the possible reasons?
Answer –
File size exceeds the limit (usually 1 GB for Pro users).
Dataset contains unsupported features or custom visuals.
Workspace permissions may be restricted.
Network issues or Power BI Service outage.
Gateway misconfiguration or unsupported data source.
Why is your Power BI report slow in Power BI Service?
Answer –
Inefficient DAX measures or complex visualizations.
Large dataset size without proper filtering or summarization.
Too many visuals or pages in the report.
Use of DirectQuery or live connections with slow response times.
Improper relationships or data model design.
Why is your Power BI dataset refresh failing intermittently?
Answer – Unstable network or inconsistent data source availability.
Gateway timeout or memory limitations.
Expired or changed credentials.
Source queries are taking too long to execute.
Schema changes in source data not reflected in Power BI model.
Why are your Power BI visuals not updating after the data refresh?
Answer – Visuals may be cached — try refreshing the browser or clearing cache.
Relationships in the model may be broken.
DAX measures may not reflect new data due to filters or context.
Data did refresh but visuals didn’t update — use F5 or Refresh Visuals manually.
The report may be connected to an older dataset or incorrect workspace.
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