Essential Power BI Concepts for Developers Quiz

Explore the most important Power BI definitions, data modeling practices, and functions every developer should know. Designed for effective interview prep and practical project readiness.

1. Understanding Data Models

   In Power BI, what best describes a Data Model?

   1. A structured way of organizing tables, relationships, and measures
   2. A single visualization or chart
   3. A data source external to Power BI

   Explanation: A Data Model organizes data using tables, relationships, calculated columns, and measures. A single visualization is just a visual representation, not a model. An external data source provides data but is not itself a data model.

2. Role of Power Query

   What is Power Query primarily used for in Power BI?

   1. Extracting, transforming, and cleaning data before report creation
   2. Exporting reports to external formats
   3. Performing calculations within Power BI visuals

   Explanation: Power Query is designed for ETL tasks—extracting, transforming, and loading data. It does not handle report exporting or perform in-visual calculations; that's the role of DAX and export features.

3. DirectQuery vs. Import Mode

   Which statement accurately distinguishes DirectQuery from Import Mode in Power BI?

   1. Import Mode connects directly to data without storing it
   2. DirectQuery accesses source data in real-time; Import Mode stores data in Power BI
   3. DirectQuery only works with cloud data sources

   Explanation: DirectQuery provides real-time access to data, while Import Mode caches/stores the data. Import Mode does not connect without storing. DirectQuery also supports both cloud and on-premises sources with the right setup.

4. Understanding Measures vs. Calculated Columns

   What is the difference between a Measure and a Calculated Column in Power BI?

   1. Measures are used only in Power Query
   2. Both are updated only during data refresh
   3. A Measure computes dynamic values; a Calculated Column is precomputed and static

   Explanation: Measures calculate values dynamically as report context changes, while Calculated Columns are computed once when data loads and remain static. Not both are refreshed only on load, and Measures are not part of Power Query.

5. Purpose of Row-Level Security (RLS)

   How does Row-Level Security (RLS) enhance data protection in Power BI?

   1. Encrypts report files for all users
   2. Restricts data access so each user only sees relevant information
   3. Prevents export of data from Power BI reports

   Explanation: RLS limits data visibility by user roles, showing only relevant data. It does not encrypt files or block exporting data, although those are separate security features.

6. Data Relationships in Power BI

   What does a One-to-Many (1:M) relationship represent in a Power BI data model?

   1. A calculation between two columns
   2. One record in Table A relates to multiple records in Table B
   3. Multiple records in Table A relate to a single record in Table B

   Explanation: A One-to-Many relationship connects a unique entry in one table with several related entries in another table. The reverse (Many-to-One) is not described this way, and a calculation between columns is unrelated to relationships.

7. Power BI Visualizations

   Which of the following is considered a Power BI visualization?

   1. Row-level security rules
   2. Bar charts and pie charts
   3. Data source credentials

   Explanation: Visualizations are graphical data displays like charts and maps. Security rules manage access, and credentials relate to connecting to data, not visual representation.

8. Use of the CALCULATE() DAX Function

   What is the main purpose of the CALCULATE() function in Power BI DAX?

   1. Create new columns in Power Query
   2. Modify the context for calculations
   3. Export report data to Excel

   Explanation: CALCULATE() adjusts the context for DAX calculations, enabling advanced aggregations. It does not create columns nor handle exporting of data.

9. Composite Model Significance

   Why is the Composite Model useful in Power BI data integration?

   1. It allows combining both DirectQuery and Import Mode in one model
   2. It is used for exporting data to external systems
   3. It only supports a single data source

   Explanation: The Composite Model lets developers blend live connections and cached data for flexibility. It doesn't restrict to one source or involve data export.

10. Slicer's Functionality

    How does a Slicer enhance Power BI report interactivity?

    1. It updates column calculations automatically
    2. It merges two datasets automatically
    3. It enables users to filter data interactively within a report

    Explanation: A Slicer is a visual tool for users to interactively filter data. It does not merge datasets nor update column calculations.