100 Questions and Answers for Power BI, DAX, and Power Query

This comprehensive list is perfect for anyone preparing for Power BI-related roles or looking to enhance their expertise in Microsoft’s data stack. We’ve broken down the questions into three major categories: Power BI, DAX (Data Analysis Expressions), and Power Query (M Language).

Power BI

1. What is Power BI?
A Microsoft business analytics tool for interactive data visualization and business intelligence.

2. What are the components of Power BI?
Power BI Desktop, Power BI Service, Power BI Mobile, Power BI Report Server, Power BI Gateway.

3. What data sources can Power BI connect to?
Excel, SQL Server, Web, APIs, SharePoint, Google Analytics, and many more.

4. What is Power BI Desktop used for?
To build and design reports and dashboards.

5. What is the Power BI Service?
A cloud-based platform to share, collaborate, and publish Power BI content.

6. What is a Power BI Gateway?
A bridge for secure data transfer between on-premises data and the Power BI Service.

7. What are Power BI datasets?
Data models created using Power BI Desktop, which are published to Power BI Service.

8. Can Power BI handle real-time data?
Yes, using streaming datasets and APIs.

9. What is a report in Power BI?
A collection of visualizations (charts, tables, KPIs) built on a single dataset.

10. What is a dashboard in Power BI?
A single-page, interactive view composed of visualizations pinned from one or more reports.

11. How do you schedule data refresh in Power BI?
Via the Power BI Service using a data gateway.

12. What is row-level security (RLS)?
A technique to restrict data access for specific users.

13. What is drill-through in Power BI?
Allows users to right-click on a data point to navigate to a detailed report.

14. What is drill-down?
Navigating deeper levels of data within a visual.

15. What is Q&A in Power BI?
A feature that lets users type natural language questions and get visual answers.

16. Can Power BI export reports to PDF or PowerPoint?
Yes.

17. What are bookmarks?
Used to capture the current view of a report page.

18. What is a slicer in Power BI?
A visual filter used to narrow down report data.

19. How do you manage relationships in Power BI?
Via the data model view using cardinality and cross-filter direction.

20. What is the default file extension for Power BI reports?
.PBIX

21. What is data modeling in Power BI?
Designing relationships, measures, and hierarchies between tables.

22. What are custom visuals?
Visuals imported from the marketplace or developed using TypeScript.

23. What is Power BI Embedded?
An Azure service for integrating Power BI visuals into custom apps.

24. How can Power BI be used with Excel?
Import data from Excel or export Power BI reports to Excel.

25. What are themes in Power BI?
Custom color palettes for consistent styling.

26. Can you use R or Python in Power BI?
Yes, for advanced analytics and custom visuals.

27. What is the selection pane?
Helps organize visuals for layering and interactivity.

28. What is sync slicer?
Synchronizes slicers across multiple report pages.

29. How do you create a KPI visual in Power BI?
Using the KPI visual and selecting value, target, and trend.

30. What is the Performance Analyzer?
A tool to measure visual load times and optimize report performance.

31. What is publish to web in Power BI?
Feature to publicly embed reports (note: removes RLS).

32. What is a tooltip in Power BI?
Hover-over information pop-up for a data point.

33. What is a calculated column?
A new column added using DAX formulas.

34. What is a measure?
A DAX expression calculated on aggregation, not stored in memory.

35. Can Power BI work offline?
Power BI Desktop can; Power BI Service requires internet.

36. How do you create hierarchies in Power BI?
Drag fields into a single field to define levels.

37. What is the difference between Power BI Free and Pro?
Pro supports sharing, collaboration, and scheduled refresh.

38. How do you optimize Power BI performance?
Reduce columns, use aggregations, disable unnecessary visuals, optimize DAX.

39. What is DirectQuery vs Import Mode?
DirectQuery fetches live data; Import loads data into memory.

40. What is composite model?
Combines DirectQuery and Import data sources.

DAX – Data Analysis Expressions

41. What is DAX?
A formula language used in Power BI, Excel, and SSAS for data modeling.

42. How is DAX different from Excel formulas?
DAX is designed for data models and works with relationships and contexts.

43. What is a calculated column in DAX?
A column computed row-by-row using DAX.

44. What is a measure in DAX?
A dynamic calculation that aggregates data based on context.

45. What is filter context in DAX?
The current filters applied to data during calculations.

46. What is row context?
Refers to the current row in a table during calculations.

47. What is CALCULATE()?
Changes filter context to perform custom calculations.

48. What is SUMX()?
An iterator that sums expressions row by row.

49. What is ALL()?
Removes filters from columns/tables.

50. What is RELATED()?
Fetches values from a related table.

51. What is RELATEDTABLE()?
Returns a table of related rows.

52. What is the difference between SUM() and SUMX()?
SUM adds a column; SUMX evaluates row by row.

53. What does DISTINCT() do?
Returns unique values in a column.

54. What is VALUES()?
Returns a one-column table of distinct values.

55. What is HASONEVALUE()?
Checks if a single value exists in a context.

56. What is IF() in DAX?
A conditional logic function.

57. What is SWITCH()?
Simplifies multiple conditions.

58. What is a virtual table?
A table created on the fly in a DAX expression.

59. What are iterators in DAX?
Functions like SUMX, AVERAGEX, MINX that evaluate row by row.

60. What is USERELATIONSHIP()?
Activates an inactive relationship in calculations.

61. What is PATH()?
Used for hierarchical paths in parent-child relationships.

62. How do you handle blank values in DAX?
Using IF/ISBLANK/COALESCE functions.

63. What is EARLIER()?
Used to reference an earlier row context.

64. What is VAR in DAX?
Defines temporary variables to simplify code.

65. What is DIVIDE()?
Performs division and handles divide-by-zero errors.

66. What is SELECTEDVALUE()?
Returns the selected value when only one exists.

67. What is RANKX()?
Ranks values over a table.

68. What is CONCATENATEX()?
Concatenates values across rows with a delimiter.

69. What is CROSSJOIN()?
Returns all combinations of rows from multiple tables.

70. What is NATURALINNERJOIN()?
Joins tables using common columns.

71. What is a semi-additive measure?
Aggregates correctly across one dimension but not another (e.g., Inventory).

72. What is ISFILTERED()?
Returns TRUE if a column is filtered.

73. What is TOTALYTD()?
Calculates year-to-date totals.

74. What is SAMEPERIODLASTYEAR()?
Returns the same period in the previous year.

75. What is TIMEINTELLIGENCE()?
Functions that help analyze data over time.

Power Query – M Language

76. What is Power Query?
A data transformation tool built into Power BI and Excel.

77. What language does Power Query use?
M (Mashup) Language.

78. How do you open Power Query Editor?
From Home > Transform Data in Power BI Desktop.

79. What is applied steps pane?
A list of all transformations applied to the query.

80. What is a query in Power Query?
A set of steps that connect to and transform data.

81. What is the difference between Power Query and DAX?
Power Query is for data prep; DAX is for analysis.

82. What are parameters in Power Query?
User-defined inputs that make queries dynamic.

83. What is merging in Power Query?
Joining two queries based on a key column.

84. What is appending in Power Query?
Stacking rows from two or more queries.

85. What is the use of Remove Duplicates?
Eliminates repeated rows based on selected columns.

86. What is the use of the Column From Examples?
Creates new columns by inferring transformations from examples.

87. What is the formula bar in Power Query?
Shows the M code for each applied step.

88. Can you write custom M code?
Yes, in the Advanced Editor.

89. What is buffering in Power Query?
Improves performance by storing query results.

90. How do you filter data in Power Query?
Using the filter dropdown or M functions.

91. What are data types in Power Query?
Text, Number, Date, Boolean, etc.

92. What is a function in Power Query?
Reusable logic defined using let and in.

93. What is the let expression?
Defines variables for use within a query.

94. What is the in expression?
Returns the final output of the query.

95. What are the common M functions?
Table.SelectRows, Table.AddColumn, Record.Field, etc.

96. Can Power Query combine multiple Excel files?
Yes, using folder connector and transformations.

97. How do you unpivot columns?
Select columns > Unpivot Columns.

98. What is query folding?
Pushing transformations back to the source for performance.

99. What is refresh preview in Power Query?
Updates the sample data to show changes.

100. Can Power Query connect to APIs?
Yes, using Web.Contents and custom headers.

This guide is designed to be your go-to resource for interview prep and professional development in Power BI, DAX, and Power Query.