Power BI Interview Questions and Detailed Answers with Project Examples
Power BI Basics
What is Power BI? Power BI is a Microsoft Business Intelligence tool that enables users to connect to, visualize, and analyze data from multiple sources. Example: In my last project, I used Power BI to consolidate sales data from SQL Server and Excel files into interactive reports that empowered the sales team to monitor performance region-wise.
What are the primary components of Power BI? Key components include Power BI Desktop, Power BI Service, Power Query, Power Pivot, Power View, Power Map, and Power Q&A. Example: I developed reports using Power BI Desktop, used Power Query for ETL, and distributed dashboards via Power BI Service ensuring stakeholders had up-to-the-minute data.
Difference between Power BI Desktop and Power BI Service? Desktop is primarily for report creation and modeling, Service is the cloud platform for report sharing, collaboration, and scheduled refreshes. Example: I built complex data models and visuals in Desktop and published reports to Service for executives and team members to access online securely.
What data sources does Power BI support? Supports files (Excel, CSV, JSON), databases (SQL Server, Oracle), web services (Salesforce, Google Analytics), cloud sources (Azure), etc. Example: I imported marketing data from Salesforce and sales data from SQL Server to blend and analyze campaign ROI.
What are the different views in Power BI Desktop? Three views: Report view (for building visuals), Data view (to inspect tables), and Model view (to manage table relationships). Example: Used Model view heavily to create and manage the star schema for the sales dataset.
What is a Power BI dashboard? A dashboard is a single-page view of pinned visuals across one or more reports and datasets consolidated for quick insights. Example: Created a sales dashboard aggregating charts pinned from sales and inventory reports shown to senior management.
Difference between report and dashboard? Reports can span multiple pages with detailed visuals; dashboards are single-page, composite views of key metrics. Example: Reports detailed sales trends while dashboards provided executives real-time KPI summaries.
What is a tile in Power BI? A tile is a visual container pinned to a dashboard from a report or dataset. Example: Pinned a bar chart comparing monthly sales per region as a tile on the sales dashboard.
Explain Power Query. Power Query is a data connection and transformation tool used to extract, transform, and load (ETL) data into Power BI. Example: Used Power Query to filter last year’s sales data, remove unnecessary columns, and merge product info with sales records.
What is Power Pivot? Power Pivot is the data modeling engine inside Power BI that enables building relationships and creating calculated columns and measures using DAX. Example: Created relationships between product, sales, and customer tables and used DAX for complex KPIs like profit margin.
Data Connectivity and Refresh
What is the difference between Import and DirectQuery mode? Import loads data into Power BI for fast performance but requires refreshes. DirectQuery queries the source live, ideal for very large or real-time databases. Example: Used Import for static historic sales data; DirectQuery connected directly to an Azure SQL database for inventory to get live status.
What is Live Connection? Live connection is similar to DirectQuery but connects only to Analysis Services or Power BI datasets without storing data in PBIX file. Example: Connected live to an SSAS tabular model maintained by the data warehouse team for enterprise finance reports.
How do you schedule data refresh in Power BI? Scheduled refreshes are set in Power BI Service with credentials that allow datasets to update on a specified frequency. Example: Set nightly refresh to update sales data from an on-premises SQL Server via Power BI Gateway.
What is Power BI Gateway? A bridge that securely transfers data between on-premises sources and Power BI cloud to enable scheduled refresh and live queries. Example: Installed and configured gateway to refresh internal SharePoint and SQL Server data for HR reports in the cloud.
What are different data refresh types in Power BI? Package refresh (for OneDrive/SharePoint), data/model refresh (scheduled updates), tile refresh (dashboard cache), visual container refresh. Example: Custom visual container refreshes ensured dashboards showed updated sales KPIs as soon as new data loaded.
Data Modeling and DAX
What is DAX? Data Analysis Expressions (DAX) is a formula language for creating custom calculations, aggregations, and filters for analysis in Power BI. Example: Created a measure to calculate Year to Date (YTD) sales dynamically using DAX.
Difference between calculated columns and measures? Calculated columns are computed for each row during load, measures compute values dynamically based on filter context. Example: Created a calculated column for product categories and a measure for total sales to sum relevant rows dynamically.
Explain row context and filter context in DAX. Row context applies operations on each row individually; filter context applies filters from slicers or visuals affecting the current calculation. Example: Used filter context with CALCULATE to compute sales only for specific regions selected in slicers.
What is CALCULATE() function used for in DAX? To change or modify filter context in a calculation. Example: Used CALCULATE to find total sales for the last year regardless of current report filters.
What is a star schema and why use it? A data modeling layout where one central fact table connects to multiple dimension tables, optimizing query speed and usability. Example: Designed fact and dimension tables in Power BI model for sales data; this improved report performance and clarity.
What are relationships in Power BI? Links that connect tables on common columns to enable cross-table filtering and analysis. Example: Created relationships linking sales fact table to customer and product dimension tables using customer ID and product ID.
Explain bi-directional filter and its use. Filters flow both ways between tables enabling complex slicers or hierarchies but can cause ambiguity. Example: Used bi-directional filtering when sales and product tables required mutual filtering for regional analysis.
What is an inactive relationship? A relationship defined but not used by default in filtering; activated in calculations via DAX. Example: Used USERELATIONSHIP in DAX to calculate sales based on an alternative date table.
What are calculated tables? Tables created using DAX formulas rather than imported from data sources. Example: Created a calculated table summarizing top 10 customers by revenue for a dashboard filter.
Explain common DAX functions like RELATED, FILTER, ALL. RELATED fetches related table values. FILTER applies row filters. ALL removes filters for calculations like totals. Example: Used FILTER and ALL in a DAX measure to calculate percent of total sales excluding current slicer filters.
Visualization and Interaction
What types of visualizations does Power BI support? Bar, column, line, pie, donut, scatter, map, table, matrix, KPI, card, funnel, waterfall, and custom visuals. Example: Used map visuals to show regional sales distribution and waterfall charts for profit margin analysis.
What is a slicer and how is it different from a filter? A slicer is an interactive visual for selecting filter values on reports; filters are set in the pane and not always visible. Example: Used slicers for product categories on sales reports to enable dynamic user filtering.
Explain drill-down and drill-through features. Drill-down explores deeper levels in a hierarchy within a visual. Drill-through takes users to a detailed report page filtered by selected data. Example: Allowed users to drill-down sales from year to month, and drill-through from overall sales chart to detailed orders.
What are bookmarks and how are they used? Saved report states with specific filters and visuals view, used for storytelling and presentations. Example: Created bookmarks to demonstrate quarterly sales trends with visual highlights during leadership meetings.
How do you create dynamic titles in Power BI? Using DAX measures producing text that changes based on slicers or filters. Example: Created a title measure “Sales for Selected Year: 2024” that updates automatically based on year selected.
What are tooltips and how can they be customized? Small pop-ups on hover showing additional info; can be customized with report pages for rich details. Example: Custom tooltip pages showed customer demographics when hovering over sales bars.
Filters and Security
Types of filters in Power BI? Report level, page level, visual level filters. Example: Applied page-level filter to show only last 3 years’ data across that page’s visuals.
What is Row-Level Security (RLS)? RLS restricts data visibility by user roles using DAX filters on tables. Example: Configured RLS so sales managers see only their territory’s data in reports.
How do you implement RLS? Define roles and DAX filter expressions in Power BI Desktop, assign users in Service. Example: Created a ‘Region Manager’ role filtering sales table by region code and assigned AD groups.
What is bi-directional filtering and why use cautiously? Enables filter flow both ways between two tables but can cause circular relationships and performance issues. Example: Used cautiously when building complex customer-product relationship models.
Power BI Service and Sharing
What is Power BI Service? Cloud SaaS platform for sharing reports, dashboards, scheduling refresh, and collaboration. Example: Published reports to workspace and shared dashboards with executives with scheduled refresh.
What are workspaces? Containers called workspaces hold datasets, reports, dashboards for teams/groups. Example: Created separate development and production workspaces to manage report lifecycle.
What are apps in Power BI? Packaged workspaces with reports and dashboards deployed to end users. Example: Published sales analysis app to the sales team for simplified report access.
Difference between sharing and publishing? Sharing grants access to specific users; publishing uploads and makes report public (within tenant). Example: Shared financial reports with CFO securely, published marketing dashboards to a broader audience.
What is Dataflow in Power BI? Cloud ETL process to prepare reusable data entities for multiple datasets. Example: Built a dataflow to preprocess customer data for several finance and marketing reports.
What is Power BI Premium? Capacity-based licensing providing dedicated resources, larger dataset sizes, paginated reports, AI features. Example: Upgraded to Premium to handle large datasets and provide faster refresh for enterprise teams.
What is the difference between Pro and Premium licenses? Pro licenses per user; Premium provides organizational capacity and advanced features. Example: Pro for individual report authors; Premium enabled enterprise-wide self-service BI scalability.
Performance and Optimization
What is Query Folding? Power Query steps translate to SQL or native source queries to reduce data transferred and speed up processing. Example: Verified query folding to SQL Server minimized load time by pushing filters to source.
What are aggregations in Power BI? Summary tables to speed queries on large datasets by pre-aggregating data. Example: Created monthly sales aggregates for faster sales trend reports.
How to optimize DAX for performance? Avoid complex row-by-row calculations, use variables, filter early, avoid unnecessary context transitions. Example: Refactored slow CALCULATE formulas to use variables, reducing report load time.
What is incremental refresh? Refreshes only new or changed data partitions instead of full refresh for large datasets. Example: Enabled incremental refresh on order data reduced refresh from 3 hours to 20 minutes.
How does VertiPaq compression improve performance? It compresses data highly in memory tabular storage improving performance and reducing memory usage. Example: Removed unwanted columns and combined similar fields for better compression ratios.
Troubleshooting and Advanced
How to troubleshoot slow reports? Use performance analyzer, check model size, optimize DAX and queries, reduce visuals on page. Example: Identified expensive visuals and replaced them with aggregated KPI cards based on analyzer output.
What are paginated reports? Pixel-perfect reports (like SSRS) ideal for printing or exporting detailed reports, supported in Power BI Premium. Example: Delivered detailed invoice reports to external auditors using paginated reports.
What is Analyze in Excel? Feature allowing PivotTable/live connection to Power BI datasets for ad hoc analysis in Excel. Example: Finance team used Analyze in Excel to build custom reports from published Power BI datasets.
What is a composite model in Power BI? A composite model allows combining Import and DirectQuery modes in a single report for flexibility and performance. Example: Used composite model to import sales history and DirectQuery for live inventory, balancing performance and real-time needs.
What is a dataflow? Dataflow is a cloud-based ETL process that prepares and stores reusable data entities for consumption by multiple datasets. Example: Created dataflows to standardize customer data cleaning steps shared across marketing and sales reports.
How do you create a hierarchy in Power BI? Drag and drop fields (e.g., Year, Quarter, Month) in Model or Report View to create drillable hierarchies. Example: Built date hierarchy enabling executives to drill into sales by year, quarter, and month.
Explain field parameters and their use. Field parameters allow dynamic changing of fields in visuals through slicers or filters for adaptability. Example: Created a parameter letting users switch sales metrics from units sold to revenue measurement in visuals.
How do you hide columns or tables? Right-click the field or table and select “Hide” from report view to simplify user experience. Example: Hid technical keys and intermediate calculation columns to keep reports clean.
What is the difference between a matrix and a table? Matrix supports grouped rows and columns with drill-down; table is a simple flat data grid. Example: Used matrix for financial reports with collapsible accounts hierarchy; tables for flat transaction logs.
What is a disconnected table? A table not linked via relationships but used for slicers or for ‘what-if’ analysis. Example: Created disconnected table to enable dynamic scenario selection in sales forecasting reports.
What is the use of USERELATIONSHIP() in DAX? Activates an inactive relationship during calculation for flexible measures. Example: Used USERELATIONSHIP to analyze sales by shipping date instead of order date.
How does Power BI handle time intelligence? Through DAX functions like SAMEPERIODLASTYEAR, TOTALYTD, PREVIOUSMONTH working on continuous date dimension. Example: Implemented YTD sales reporting using DAX and date table in all financial dashboards.
What is a calculated measure? A metric computed on-the-fly based on filters, different from calculated columns which are stored. Example: Created measure ‘Average Sales Per Customer’ filtering dynamically by selected regions.
Difference between slicer and filter visual? Filters are static elements set per visual or page, slicers are interactive visuals for users to filter report dynamically. Example: Provided slicers for product categories to enable end-user filtering on sales dashboards.
What is a hierarchy slicer? A slicer that supports hierarchical display, allowing users to select at different levels. Example: Built hierarchy slicer for geography enabling country, state, or city level filtering on reports.
What are aggregations? How do they improve performance? Pre-aggregated summary tables that reduce volume of source data scanned for queries. Example: Used monthly aggregated sales table to speed up dashboard load for large datasets.
Explain incremental refresh and partitioning. Incremental refresh loads only new or changed partitions reducing refresh time. Example: Partitioned customer transactions by year and refreshed only current year data daily.
What is a gateway cluster? Multiple gateways running collectively for high availability and load balancing. Example: Set up gateway cluster to ensure uninterrupted data refreshes when one gateway server was down.
What is Power BI Premium per User? Premium licensing for individual users with access to premium features like larger models and advanced AI. Example: Purchased Premium Per User license for a lead analyst handling large datasets.
How do you optimize DAX queries? Use variables, reduce filter complexity, evaluate CALCULATE usage, prefer aggregations. Example: Simplified a user’s slow measure by replacing nested CALCULATE with variables, improving report speed.
Explain Analyze in Excel feature. Enables connecting Excel pivot tables to Power BI datasets for advanced data exploration. Example: Enabled the finance team to analyze corporate expenses using Excel pivot tables connected live to Power BI data.
What is the cloud deployment pipeline in Power BI? A feature to manage report lifecycle from development through test to production environments. Example: Used deployment pipeline to push changes incrementally from development workspace to production workspace.
What are Power BI template files (.pbit)? Templates saving report structure, queries, and model but without data for reuse. Example: Created templates for monthly sales reports that teams could personalize with their data.
What is sensitivity labeling? Applying classification labels to data ensuring compliance with privacy and governance policies. Example: Labeled confidential financial reports to restrict access and prevent unauthorized sharing.
Can you explain composite models? Models combining Import and DirectQuery data connectivity modes in same report. Example: Used composite models to mix cached historical and real-time transactional data.
What is paginated report? Pixel-perfect, print-ready reports created with Power BI Report Builder, ideal for invoices and forms. Example: Delivered detailed monthly billing statements to customers using paginated reports.
How do you secure reports in Power BI? RLS, sharing permissions, sensitivity labels, avoid publish to web for private data. Example: Applied RLS and assigned viewer roles to ensure only authorized users saw sensitive HR data.
What are drillthrough reports? Reports linked so clicking on a summary navigates to detail page filtered by selected item. Example: Clicked on a product category to open detailed sales invoice report specific to that product.
What is Q&A visual in Power BI? Natural language search box allowing users to ask questions and get dynamic visuals. Example: Enabled executives to get instant answers by typing “Total sales in 2024 by region” into Q&A.
What is a KPI visual? Displays a key metric with comparison to target showing status in colors (red, yellow, green). Example: Used KPI cards for sales targets meeting status across different teams.
How to enable bookmarks and what are its use cases? Bookmarks save report view settings to create storyboards or toggle between states. Example: Developed a guided sales tour report using bookmarks to highlight quarterly key facts.
What is the use of natural language query in Power BI? Users can ask plain English queries to create visuals automatically (powered by Q&A). Example: Integrated Q&A for business users to quickly generate charts without report editing.
How to handle version control in Power BI projects? Save PBIX files in source control systems like Git with clear commit messages. Example: Maintained versioned code of report PBIX files in Git repository for collaborative development.
What is a disconnected slicer? Slicer with no relationship to model tables, often used with DAX to control measures. Example: Created disconnected slicer to switch between sales metrics like quantity or revenue dynamically.
What is field parameter in Power BI? Allows users to swap fields dynamically in visuals via slicers. Example: Enabled report users to switch revenue, profit, or margin in charts using field parameters.
Explain the use of custom visuals in Power BI. Custom visuals are user-imported visuals for specific use cases unavailable in default set. Example: Imported a custom heatmap visual to better display product performance geographically.
What is the Analyze feature in Power BI? A feature to drill into insights automatically generated by AI-powered visual analysis. Example: Used Analyze to identify top customers impacting sales growth without manual calculations.
What are data alerts in Power BI? Email or mobile notifications triggered by thresholds set on numeric tiles on dashboards. Example: Set alerts for sales drop below target so sales managers could react immediately.
How does Power BI integrate with Excel? Can export data, create Analyze in Excel connections, and embed Excel reports inside Power BI. Example: Finance analysts explored Power BI datasets live through Excel pivot tables.
What is the use of R and Python in Power BI? Embed R and Python scripts for advanced analytics and custom visuals. Example: Used Python scripts for sophisticated clustering analysis visualized within reports.
How do report-level filters work? Filters applied across the entire report affecting all pages and visuals. Example: Applied report-level filter to restrict report only to current financial year data.
What is the difference between filtering and slicers? Filtering can be applied silently to visuals or pages; slicers are visible and interactive filter controls. Example: Used both to restrict visuals but provide user control when needed.
How do you handle incremental refresh on dataflows? Configure dataflows to refresh only partitions of data based on date/time parameters. Example: Setup customer activity dataflow to only refresh new rows to save time.
What are measure tables in Power BI? Tables created solely to organize calculated measures, without any data rows. Example: Created a dedicated “Measures” table to keep all KPI measures centralized.
Difference between fact and dimension tables? Fact table contains quantitative data and keys; dimension tables contain descriptive attributes. Example: Sales fact table recorded transactions; product dimension table stored product names and categories.
Why use star schema over snowflake? Star schemas simplify design, improve query performance, and are best suited for Power BI optimization. Example: Transformed a snowflake schema into star with denormalized product info to improve report speed.
What is role-playing dimension? A table with multiple relationships to fact table for different roles (e.g., order date vs delivery date). Example: Used role-playing date dimension to analyze sales by order and shipping dates.
What is a KPI indicator? Visual showing performance metric against a goal with trend and status (e.g., traffic light). Example: Developed KPIs for monthly sales vs target with color coding for quick status insight.
How do you troubleshoot refresh failures? Check gateway, data source connectivity, credentials, query errors, refresh logs in Power BI Service. Example: Investigated gateway errors for failed SQL scheduled refresh and corrected firewall rules.
How do you handle large data import limits? Use Premium capacity, DirectQuery, incremental refresh, aggregations, or split data sources. Example: Split huge sales data across yearly datasets and used aggregated models to overcome size limits.
How do you publish a Power BI report to web? Use “Publish to web” feature to generate public URL or embed code (not for confidential data). Example: Shared company public sustainability report broadly via a publish-to-web link.
How is sensitivity labeling applied? Labels classify reports/datasets to enforce governance, restrict sharing, and protection policies. Example: Classified HR data reports with high sensitivity label restricting sharing outside HR group.
What are common best practices for Power BI development? Model star schemas, use incremental refresh, optimize DAX, minimize visuals per page, use roles and security, document reports. Example: Followed all best practices for a finance dashboard project which reduced refresh time by 70% and improved usability.
