Question: You created a Power BI sales dashboard using data from Excel and SQL Server. The dashboard isn’t refreshing in the Power BI Service. What could be the issue?
Answer:
Possible reasons:
· Gateway not configured for on-premises SQL Server.
· Credentials missing or expired in data source settings.
· Refresh schedule not set or it failed.
Fix:
· Install and configure On-Premises Data Gateway.
· Go to Power BI Service > Settings > Dataset > Edit Credentials.
· Review refresh logs for specific errors.
Queries: Power BI refresh issue, data gateway error, Power BI service troubleshooting
Question: Why does your Power BI matrix visual show incorrect totals for a DAX measure?
Answer:
The issue often occurs because DAX measures behave differently at aggregate levels. For example:
SalesPerCustomer = [Total Sales] / DISTINCTCOUNT(Customer[CustomerID])
This works at row level but gives incorrect total because DISTINCTCOUNT is recalculated for the grand total. Use:
SalesPerCustomerFixed =
DIVIDE([Total Sales], CALCULATE(DISTINCTCOUNT(Customer[CustomerID]), ALLSELECTED(Customer)))
Queries: Power BI total mismatch, DAX total fix, matrix total error
Question: You want a slicer to affect only one visual on the report. How do you achieve that?
Answer:
Use Edit Interactions:
1. Select the slicer.
2. Go to Format → Edit interactions.
3. Disable interaction for the visuals you don’t want affected.
Queries: Power BI slicer control, edit visual interactions, filter one visual only
Question: You want regional managers to see only their own data in a shared report. What feature do you use?
Answer:
Use Row-Level Security (RLS):
· Define roles in Power BI Desktop using DAX filters.
· Example: [Region] = USERNAME()
· Assign roles in Power BI Service under dataset settings.
Queries: Power BI row-level security, dynamic RLS, user-based data filtering
Question: Your report takes too long to load. What performance improvements can you apply?
Answer:
· Reduce visual count on pages.
· Avoid complex DAX inside visuals.
· Use aggregated tables for large datasets.
· Optimize queries in Power Query Editor.
· Use Performance Analyzer to debug.
Queries: Power BI performance tuning, optimize slow report, DAX performance tips
Question: How do you merge Excel and SQL Server data in Power BI?
Answer:
· Load both data sources into Power Query.
· Use Merge Queries or Append Queries.
· Ensure column data types match for successful joins.
· Use relationships if data isn’t merged.
Queries: Power BI merge queries, combine Excel and SQL Server, multi-source data modeling
Question: Your DAX time intelligence functions like YTD() aren't working. What’s wrong?
Answer:
Time intelligence requires a dedicated, continuous Date Table:
· Create a Date Table in DAX or Power Query.
· Mark it as Date Table in the model.
· Use it in time-based DAX formulas.
Queries: Power BI date table error, time intelligence not working, mark as date table
Question: How do you show the most recent transaction per customer?
Answer:
Create a measure or calculated column using DAX:
Latest Transaction =
CALCULATE(
MAX(Transactions[Date]),
ALLEXCEPT(Transactions, Transactions[CustomerID])
)
Use it in a filter or as part of your visual logic.
Queries: Power BI latest record per group, max date DAX, show last transaction
Question: How do you create a visual title that changes based on a slicer?
Answer:
1.Create a DAX measure:
SelectedRegion = "Sales Report for " & SELECTEDVALUE(Region[RegionName], "All Regions")
2.Use it as a conditional format for the visual title.
Queries: dynamic title Power BI, DAX title change, responsive visuals
Question: How do you calculate YoY (Year over Year) growth in Power BI?
Answer:
Use DAX:
Total Sales = SUM(Sales[Amount])
Previous Year Sales = CALCULATE([Total Sales], SAMEPERIODLASTYEAR(Date[Date]))
YoY Growth % = DIVIDE([Total Sales] - [Previous Year Sales], [Previous Year Sales])
Queries: Power BI YoY growth, sameperiodlastyear example, compare years DAX
Question: How do you build a Power BI report that supports multiple languages?
Answer:
· Use translation tables for labels and titles.
· Control content via slicers or dynamic DAX.
· Power BI doesn’t natively support language switching, so use measures with SWITCH or dynamic metadata workaround.
Queries: multilingual Power BI, internationalization, language switch Power BI
Question: How do you enable or restrict exporting data from visuals?
Answer:
In Power BI Service:
· Go to report settings > Export Data.
· Enable/disable based on user roles.
You can also restrict export using sensitive data labels or object-level security.
Queries: Power BI export to Excel, data protection export, user-level control
These Power BI scenario-based interview questions and answers prepare you for real-world challenges across:
· Data modeling
· DAX logic
· Performance tuning
· Security