Top 25 Power BI interview questions and answers

Basic Power BI Interview Questions

1. What is Power BI?

Answer:
Power BI is a business intelligence (BI) and data visualization tool by Microsoft that helps users create interactive reports and dashboards. It allows users to connect to various data sources, transform data, and create insightful visualizations. It consists of the following components:

• Power BI Desktop — A Windows application for designing reports.
• Power BI Service — A cloud-based service for sharing and collaboration.
• Power BI Mobile — A mobile application for viewing reports on the go.
• Power BI Gateway — A bridge that connects on-premises data to cloud services.

2. What are the key components of Power BI?

Answer:
Power BI consists of five main components:

1. Power Query — Used for extracting, transforming, and loading (ETL) data.
2. Power Pivot — Data modeling tool for creating relationships and calculations.
3. Power View — Data visualization tool for creating interactive charts, graphs, and maps.
4. Power Map — Geospatial visualization tool for mapping data.
5. Power Q&A — Natural language processing feature that allows users to ask questions in plain English and get data insights.

3. How is Power BI different from Tableau?

Answer:

4. What is DAX in Power BI?

Answer:
DAX (Data Analysis Expressions) is a formula language in Power BI used for:

• Creating calculated columns, measures, and tables.
• Performing aggregations and complex calculations.
• Supporting filtering, ranking, and time intelligence functions.

Example:

Total Sales = SUM(Sales[SalesAmount])

5. What are the different types of filters in Power BI?

Answer:
Power BI provides three main types of filters:

1. Visual-Level Filters — Apply to a specific visual.
2. Page-Level Filters — Apply to all visuals on a page.
3. Report-Level Filters — Apply to all pages in a report.

Intermediate Power BI Interview Questions

6. What is the CALCULATE function in DAX?

Answer:
CALCULATE() is used to modify the context of a calculation using filters.

Syntax:

CALCULATE(<expression>, <filter>)

Example: Calculate total sales for “East” region:

Total Sales East = CALCULATE(SUM(Sales[SalesAmount]), Sales[Region] = "East")

7. What challenges do Power BI developers face?

Answer:

• Performance issues with large datasets.
• Data refresh limitations in Power BI Service.
• DAX complexity for advanced calculations.
• Real-time data handling challenges.

8. How do you automate Power BI reports?

Answer:

• Power Automate: Used for scheduling report refreshes and notifications.
• Scheduled Refresh: Set in Power BI Service to update data at specific intervals.
• REST API: Automates data import/export and report generation.

9. Explain the Bookmark feature in Power BI.

Answer:

• Bookmarks allow users to capture and save a report’s current state, including applied filters and slicers.
• Useful for navigating between different report views dynamically.

10. What is the Power BI Data Gateway?

Answer:

• A bridge that connects on-premises data sources with Power BI Service.
• Allows secure data transfer between Power BI and local databases.
• Required for scheduled refreshes and DirectQuery connections.

Advanced Power BI Interview Questions

11. What is Row-Level Security (RLS)?

Answer:

• RLS restricts data access based on user roles.
• Implemented using DAX filters.

Example:
If USERPRINCIPALNAME() is used in a DAX filter, users will only see data that matches their email.

DAX[Region] = USERPRINCIPALNAME()

12. How do you optimize Power BI performance?

Answer:

• Reduce data size (remove unnecessary columns, use aggregations).
• Optimize DAX formulas (use variables instead of repeated calculations).
• Use DirectQuery instead of Import mode for large datasets.
• Disable unnecessary visuals to improve dashboard loading time.

13. What is the difference between Power BI Report and Dashboard?

Answer:

14. What are Content Packs in Power BI?

Answer:

• Pre-packaged collections of reports, dashboards, and datasets.
• Shared within an organization via Power BI Service.

15. What are Custom Visuals in Power BI?

Answer:

• Custom-built charts, graphs, and visuals using JavaScript libraries like D3.js.
• Available through Power BI Visual Marketplace.

16. What data sources can Power BI connect to?

Answer:

• Files: Excel, CSV, JSON.
• Databases: SQL Server, MySQL, Oracle.
• Cloud Services: Azure, Google Analytics, Salesforce.
• APIs: REST APIs, OData.

17. What is the FILTER function in DAX?

Answer:

• Returns a subset of a table based on conditions.

Example:

FILTER(Sales, Sales[Amount] > 1000)

This returns rows where Amount > 1000.

18. What are the different types of Power BI licenses?

Answer:

1. Power BI Free — Basic report creation.
2. Power BI Pro — Sharing and collaboration features.
3. Power BI Premium — Enterprise-level scalability.

19. What is Power BI Dataflow?

Answer:

• Dataflows store and preprocess data before loading into reports.
• Allows reuse of data models across different reports.

20. How does Power BI handle real-time data?

Answer:

• Streaming datasets (push data via APIs).
• DirectQuery (connect directly to a database).
• Azure Stream Analytics (real-time IoT data).

Scenario-Based Power BI Questions

21. How would you improve the performance of a slow Power BI report?

Answer:

• Reduce dataset size.
• Use aggregations instead of row-level data.
• Optimize DAX calculations using variables.
• Limit the number of visuals per report page.

22. What would you do if a scheduled data refresh fails in Power BI Service?

Answer:

• Check data source availability.
• Verify credentials and permissions.
• Ensure gateway is running.
• Reduce data volume.

23. How do you handle a report showing incorrect data?

Answer:

• Check data source integrity.
• Verify DAX formulas and filters.
• Inspect relationships in the data model.

24. How do you secure sensitive data in Power BI?

Answer:

• Row-Level Security (RLS) for access control.
• Workspace permissions.
• Data encryption and masking.

25. How would you create a KPI indicator in Power BI?

Answer:

• Use DAX Measures for KPIs.
• Apply conditional formatting for color-coded insights.

Example:

KPI Status = IF([Sales] > 50000, "Good", "Bad")

Basic Power BI Interview Questions

1. What is Power BI and why is it used?

Answer:
Power BI is a Business Intelligence (BI) tool by Microsoft that helps organizations analyze data and create interactive reports and dashboards. It allows:

• Data connectivity from multiple sources.
• Data transformation and modeling.
• Visualization for better decision-making.

2. What are the key components of Power BI?

Answer:

1. Power BI Desktop — Local development tool for creating reports.
2. Power BI Service — Cloud platform for sharing and collaboration.
3. Power BI Mobile — Access reports on mobile devices.
4. Power BI Data Gateway — Connects on-premises data to cloud services.
5. Power BI Report Server — On-premises report hosting.

3. What are the different views in Power BI Desktop?

Answer:

• Report View — Create and customize visualizations.
• Data View — Explore and transform data.
• Model View — Define relationships between tables.

4. What are the different file formats supported in Power BI?

Answer:

• .PBIX — Power BI Desktop files.
• .PBIT — Power BI template files.
• .CSV/.XLSX — Data import files.
• .JSON — Custom data source files.

5. How does Power BI connect to data sources?

Answer:
Power BI can connect to:

• Files: Excel, CSV, XML, JSON.
• Databases: SQL Server, MySQL, PostgreSQL, Oracle.
• Cloud Services: Azure, Google Analytics, Salesforce.
• APIs: REST, OData.

Intermediate Power BI Interview Questions

6. What is DirectQuery vs Import Mode in Power BI?

Answer:

7. What is Power Query?

Answer:
Power Query is an ETL tool that allows:

• Extracting data from various sources.
• Transforming data (cleaning, merging, splitting).
• Loading data into Power BI.

8. What is Power Pivot?

Answer:
Power Pivot is an in-memory data modeling component that:

• Supports large datasets efficiently.
• Helps in creating relationships between tables.
• Uses DAX (Data Analysis Expressions) for calculations.

9. What is Power BI Service?

Answer:
Power BI Service is a cloud-based platform for:

• Publishing and sharing reports securely.
• Collaboration through workspaces.
• Scheduling refreshes for updated reports.

10. What is a Power BI Gateway?

Answer:
A Power BI Gateway acts as a bridge between on-premises data sources and cloud-based Power BI Service, allowing secure data transfer.

11. What are relationships in Power BI?

Answer:
Relationships define how tables are linked in Power BI models:

• One-to-Many (1:M) — Most common.
• Many-to-Many (M:M) — Requires bridge tables.
• One-to-One (1:1) — Used for specific cases.

12. What is Row-Level Security (RLS) in Power BI?

Answer:
RLS restricts data access based on user roles using DAX filters.

DAX (Data Analysis Expressions) in Power BI

13. What is DAX?

Answer:
DAX is a formula language in Power BI used to:

• Create calculated columns and measures.
• Perform aggregations and filtering.
• Support time intelligence functions.

14. Explain the CALCULATE function in DAX.

Answer:
CALCULATE() modifies calculations using filters.

Syntax:

15. What is the difference between calculated columns and measures?

Answer:

16. What are Time Intelligence functions in DAX?

Answer:
Functions used for date-based calculations:

• TOTALYTD() — Year-to-date calculations.
• PREVIOUSMONTH() — Retrieves previous month’s data.
• DATESBETWEEN() — Filters data within a date range.

17. What is the FILTER function in DAX?

Answer:
FILTER is used to extract specific data from a table.

Example:

FILTER(Sales, Sales[Amount] > 1000)

Power BI Visualization & Report Development

18. What are Power BI visualizations?

Answer:
Power BI supports:

• Bar, Line, Pie Charts.
• Tables & Matrices.
• Maps & Scatter Plots.
• Custom Visuals from the Marketplace.

19. What is the difference between a Power BI Report and a Dashboard?

Answer:

20. What is a KPI in Power BI?

Answer:
KPI (Key Performance Indicator) visualizes business performance using:

• Target value (e.g., sales goal).
• Actual value (e.g., achieved sales).
• Indicator (e.g., color-coded trends).

Power BI Performance Optimization & Security

21. How do you improve Power BI report performance?

Answer:

• Reduce dataset size (remove unused columns).
• Optimize DAX calculations using variables.
• Use aggregations instead of raw data.
• Disable unnecessary visuals.

22. What are Power BI Content Packs?

Answer:
Content Packs are pre-built datasets, reports, and dashboards shared within an organization.

23. How do you schedule a data refresh in Power BI?

Answer:

• In Power BI Service, use Scheduled Refresh.
• Requires a Power BI Gateway for on-premises data.

Scenario-Based Power BI Questions

24. What would you do if a report fails to refresh?

Answer:

• Check data source connectivity.
• Verify gateway is running.
• Adjust query load settings.

25. How would you design a sales dashboard in Power BI?

Answer:

• KPIs (Revenue, Profit, Growth Rate).
• Charts (Sales by Region, Monthly Trends).
• Filters/Slicers (Date Range, Product Category).

26. How do you handle large datasets in Power BI?

Answer:

• Use DirectQuery instead of Import Mode.
• Apply data aggregations.
• Implement incremental refresh.

27. How do you secure Power BI reports?

Answer:

• Row-Level Security (RLS).
• Workspace permissions.
• Data encryption.