30 Power BI questions. One line each.
If you can answer all of these without looking, the technical round is not your problem anymore.
Most people get stuck on 10, 11 and 12. Filter context is where interviews are won or lost.
Save it. Revise it the night before.
Basics
- 01
What is Power Query?
ETL layer of Power BI. Cleans and shapes data using the M language.
- 02
Power BI Desktop vs Service?
Desktop builds reports. Service publishes, shares and schedules refresh.
- 03
What is DAX?
Formula language for measures, calculated columns and calculated tables.
- 04
Measure vs calculated column?
Column: stored row by row at refresh. Measure: computed at query time in filter context.
- 05
Import vs DirectQuery?
Import loads data into the model (fast, needs refresh). DirectQuery hits the source live.
Data modeling
- 06
What is a star schema?
One fact table linked to dimension tables. The model Power BI is built for.
- 07
Fact vs dimension table?
Fact: numeric events (sales). Dimension: who, what, when (customer, product, date).
- 08
Relationship cardinality types?
One-to-one, one-to-many, many-to-many. One-to-many is the default you want.
- 09
Single vs both cross-filter?
Controls which way filters flow across a relationship. Use both sparingly.
- 10
Row vs filter context?
Row context iterates rows. Filter context is the set of filters applied to a calculation.
DAX core
- 11
What does CALCULATE do?
Evaluates an expression in a modified filter context. The most asked DAX function.
- 12
SUM vs SUMX?
SUM adds a column. SUMX loops a table and sums an expression per row.
- 13
What does ALL do?
Removes filters from a table or column. Used for % of total.
- 14
RELATED vs RELATEDTABLE?
RELATED pulls a value from the one side. RELATEDTABLE returns rows from the many side.
- 15
Why a separate date table?
Time intelligence needs continuous dates. Mark it as a date table.
DAX + time
- 16
Name 3 time intelligence functions
TOTALYTD, SAMEPERIODLASTYEAR, DATEADD.
- 17
What is row-level security?
Restricts rows per user through DAX roles.
- 18
How is RLS made dynamic?
Filter on USERPRINCIPALNAME() so each user sees only their data.
- 19
What is a gateway?
Bridge that lets the Service refresh data from on-premise sources.
- 20
Refresh limit: Pro vs Premium?
8 scheduled refreshes a day on Pro, 48 on Premium.
Service + reports
- 21
Report vs dashboard?
Report: multi-page, interactive, one dataset. Dashboard: one page of pinned tiles.
- 22
What are bookmarks?
Saved report states (filters, visuals) for navigation and storytelling.
- 23
What is drill-through?
Right-click a value to jump to a detail page filtered to it.
- 24
Slicer vs filter pane?
Slicer sits on the canvas for users. Filter pane works at visual, page, report level.
- 25
Merge vs Append?
Merge joins columns (like SQL JOIN). Append stacks rows (like UNION).
Reports + tuning
- 26
What is a calculated table?
A table built with DAX, e.g. a date table with CALENDAR().
- 27
What is a what-if parameter?
A slider-driven table plus measure to simulate scenarios.
- 28
How do you tune a slow report?
Star schema, drop unused columns, cut cardinality, use Performance Analyzer.
- 29
What is a KPI visual?
Shows a value against a target with a trend indicator.
- 30
How do you handle many-to-many?
Add a bridge table, or use a many-to-many relationship with care.
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30 Power BI interview questions, 1-line answers
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