Prepare for your Power BI interview with this comprehensive guide featuring 30 essential questions and answers. Organized from basic to advanced, these cover conceptual, practical, and scenario-based topics to help freshers, candidates with 1-3 years, and 3-6 years of experience succeed.
Basic Power BI Interview Questions
1. What is Power BI?
Power BI is a business analytics tool by Microsoft that enables users to visualize and share insights from data through interactive reports and dashboards.[2][4]
2. What are the major components of Power BI?
The major components include Power BI Desktop for report creation, Power BI Service for sharing and collaboration, Power BI Mobile for access on devices, and Power BI Gateway for data connectivity.[4]
3. What are the key features of Power BI?
Key features include data connectivity from multiple sources, data transformation with Power Query, interactive visualizations, DAX for calculations, and real-time dashboards.[1][2]
4. What is the difference between Power BI Desktop and Power BI Service?
Power BI Desktop is a free Windows application for creating reports and data models, while Power BI Service is a cloud platform for publishing, sharing, and collaborating on those reports.[1]
5. Name some common visualization types in Power BI.
Common types include bar and column charts for comparisons, line charts for trends, pie charts for proportions, tables for details, and maps for geographical data.[2]
6. What is a slicer in Power BI?
A slicer is an on-canvas visual that allows users to filter data interactively by selecting values from a list, date range, or hierarchy.[5]
7. How do you connect to multiple data sources in Power BI?
In Power BI Desktop, use Get Data to connect sources like Excel, SQL databases, or web files, then combine them using queries in Power Query Editor.[1]
8. What is Power Query in Power BI?
Power Query is an ETL tool in Power BI for extracting, transforming, and loading data from various sources before modeling and visualization.[3]
9. Explain Import mode versus DirectQuery in Power BI.
Import mode loads data into Power BI for fast performance, while DirectQuery queries the source database live for real-time data without storage.[2][5]
10. How do you publish a Power BI report to the service?
Open the report in Power BI Desktop, click Publish, select the workspace, and confirm to upload it to Power BI Service.[1]
Intermediate Power BI Interview Questions
11. What is DAX in Power BI? Give a simple example.
DAX (Data Analysis Expressions) is a formula language for creating measures and calculated columns. Example:
Total Sales = SUM(Sales[Amount])[1][4]
12. What is the difference between a measure and a calculated column?
A calculated column is computed row-by-row at data load time and stored in the model, while a measure is calculated dynamically based on report filters.[1]
13. What does the CALCULATE function do in DAX?
CALCULATE modifies the filter context of an expression, enabling advanced calculations like year-over-year growth.[3][5]
14. Explain the ALL function in DAX.
ALL removes filters from a table or column, returning all values regardless of slicers or filters applied in the report.[5]
15. How do you handle missing data in Power BI?
Strategies include filling with averages using Power Query, replacing blanks with zeros, or excluding rows; for dates, extend series using DAX.[1]
16. What are relationships in Power BI data models?
Relationships link tables via common keys (one-to-many or many-to-one), enabling cross-table filtering and calculations.[3]
17. How do you create a date table in Power BI?
Use DAX:
DateTable = CALENDAR(DATE(2020,1,1), DATE(2025,12,31))then mark it as a date table in the model view.[4]
18. What is Row-Level Security (RLS) in Power BI?
RLS restricts data access by defining DAX filters on roles, so users see only their authorized rows when viewing reports.[1]
19. How do you implement RLS in Power BI?
Create roles in Power BI Desktop, define DAX filters like [Region] = USERPRINCIPALNAME(), publish, and assign users in the service.[1]
20. What is the Power BI Gateway?
The gateway is software that connects on-premises data sources to Power BI Service for secure scheduled refreshes.[3][5]
Advanced Power BI Interview Questions
21. How do you optimize Power BI report performance?
Reduce data with filters, remove unused columns, use aggregations, avoid complex DAX in visuals, and prefer Import mode.[1][2]
22. Explain time intelligence functions in DAX with an example.
Functions like SAMEPERIODLASTYEAR shift dates for comparisons. Example:
Sales LY = CALCULATE(SUM(Sales[Amount]), SAMEPERIODLASTYEAR('Date'[Date]))[4]
23. What are iterator functions in DAX?
Iterators like SUMX or AVERAGEX apply expressions row-by-row over a table, returning aggregated results.[5]
24. How do you avoid circular dependencies in DAX?
Avoid mutual references between measures/columns; use CALCULATE carefully and prefer measures over calculated columns for context-dependent logic.[3]
25. Scenario: At Zoho, your report is slow with large data. What steps do you take?
Apply filters in Power Query to reduce rows, remove unnecessary columns, use aggregations, and enable query folding for efficiency.[2]
26. Scenario: Combine sales data from Paytm’s SQL database and Adobe’s CSV with inconsistent formats.
In Power Query, merge queries, standardize columns (e.g., rename, type conversions), handle nulls, and append into one table.[5]
27. How does USERELATIONSHIP function work in DAX?
USERELATIONSHIP activates an inactive relationship for a specific calculation, useful for multiple date tables.[5]
28. Scenario: At Atlassian, identify sales outliers in a report with 100 million records.
Use DAX with statistical functions like AVERAGEX and STDEVX, create a measure for z-scores, and visualize with scatter plots filtered above thresholds.[3]
29. What is Power Q&A? Give an example query.
Power Q&A allows natural language queries on visuals. Example: “total sales in 2023” generates a summarized visual automatically.[2]
30. Scenario: Migrate Oracle on-premises reports to Power BI cloud at Swiggy with live updates.
Install gateway for connectivity, use DirectQuery mode, set up scheduled refreshes or real-time streaming, and recreate visuals in Power BI Service.[5]
