Power BI Interview Questions For Intermediate Level
As professionals go through their career, they might be expected to possess a deeper understanding of Power BI, including knowing its "inner workings" and capacity. This includes not only knowing the basic features but being aware of more advanced features, data modeling techniques, and best practices in report creation and data analysis. In the following sections, we will discuss some intermediate-level interview questions on Power BI that have more to do with the intricacies of MS Power BI. These questions are aimed at assessing a candidate's ability to effectively use Power BI in a professional setting, touching on data storage, security, relationships, and performance optimization.
Q. Where is data stored in Power BI?
Data in Power BI can be stored in several ways depending on the version being used. In Power BI Desktop, data is stored in an internal model using a highly optimized columnar storage format. For users of Power BI Service, datasets are stored in Microsoft Azure, allowing for cloud-based accessibility and collaboration.
Q. What is row-level security?
Row-level security (RLS) in Power BI restricts data access at the row level based on user roles. This means that different users can see different data within the same report or dashboard, ensuring that sensitive information is only visible to authorized individuals.
Q. Why should you apply general formatting to Power BI data?
General formatting of Power BI data enhances report readability and consistency. It facilitates stakeholders to view visualizations fast and understand the insights without any confusion caused due to different formats, thereby enhancing the overall experience of the users.
Q. What are the different views available in Power BI Desktop?
Power BI Desktop offers three main views:
- Report View: For designing and building reports.
- Data View: To inspect and analyze the underlying dataset.
- Model View: For managing relationships between tables and visualizing the data model structure.
Q. What are the various versions of Power BI?
There are three main versions of Power BI:
- Power BI Desktop: A free version for creating reports and dashboards.
- Power BI Pro: A paid version that allows sharing, collaboration, and more extensive features.
- Power BI Premium: Offers enhanced performance, larger storage capacities, and advanced features for enterprise-level deployments.
Q. Explain the building blocks of Microsoft Power BI?
The building blocks of Microsoft Power BI include:
- Datasets: The data sources imported into Power BI.
- Reports: Collections of visuals based on datasets.
- Dashboards: Single-page summaries created from multiple reports.
- Workspaces: Collaborative environments for managing content and sharing insights among users.
Q. What are the critical components of the Power BI toolkit?
The critical components of the Power BI toolkit include:
- Power Query: For data extraction and transformation.
- Power Pivot: For data modeling and creating relationships.
- DAX (Data Analysis Expressions): A formula language for calculations.
- Power BI Service: The online platform for sharing and collaboration.
Q. What do you mean by the content pack?
A content pack in Power BI is a pre-packaged collection of related dashboards, reports, datasets, and Excel files that can be shared with users. Content packs can be created by organizations or sourced from third-party providers to facilitate easy access to common analytics resources.
Q. Define bi-directional cross filtering.
Bi-directional cross filtering allows filters to flow both ways between related tables in a data model. This means that when a filter is applied to one table, it affects related tables as well, enabling more dynamic interactions within visualizations.
Q. What are the three fundamental concepts of DAX?
The three fundamental concepts of DAX are:
- Filter Context: The set of filters applied to a calculation based on user selections or report filters.
- Row Context: The context of a single row when performing calculations across tables.
- Evaluation Context: The combination of filter context and row context that determines how DAX formulas are evaluated.
Q. Why and how would you use a custom visual file?
Custom visual files can be used in Power BI to enhance visualizations beyond standard options. Users can import these visuals from external sources or create their own using tools like TypeScript or D3.js to meet specific analytical needs or provide unique insights.
Q. What are some familiar sources for data in the Get Data menu in Power BI?
Common sources available in the Get Data menu include:
- Excel files
- SQL Server databases
- SharePoint lists
- Online services (like Google Analytics)
- Web APIs
Q. What are the categories of data types?
Data types in Power BI include:
- Text: For string values.
- Number: For integer or decimal values.
- Boolean: For true/false values.
- Date/Time: For date and time values.
Q. Name some commonly used tasks in the Query Editor?
Common tasks performed in Query Editor include:
- Data transformation (e.g., merging, appending queries)
- Cleaning data (e.g., removing duplicates, filtering rows)
- Changing data types for columns
- Creating calculated columns based on existing data
Q. What do you mean by grouping?
Grouping in Power BI refers to consolidating rows based on shared attributes to summarize data. This allows users to aggregate values (like sums or averages) for categories within a dataset, making it easier to analyze trends and patterns.
Q. Explain responsive slicers in Power BI.
Responsive slicers adjust their size and layout dynamically based on the available space within a report. This feature enhances user interaction by ensuring that slicers remain accessible and visually appealing across different screen sizes and devices.
Q. What is query folding in Power BI?
Query folding refers to the ability of Power Query to push transformations back to the source database rather than processing them within Power BI itself. This optimizes performance by leveraging the database's capabilities for handling large datasets efficiently.
Q. What is "M language"?
M language is a functional programming language used in Power Query for data manipulation and transformation tasks. It allows users to write complex queries for importing, shaping, and cleaning data before loading it into Power BI.
Q. Can you give an example of a DAX function?
An example of a DAX function is SUM(), which calculates the total sum of a column's values. For instance, Total Sales = SUM(Sales[SalesAmount]) computes the total sales amount from the Sales table.
Q. Explain the difference between a calculated column and a measure.
A calculated column is computed during data load and stored within the model as part of the table; it evaluates row-by-row. A measure calculates results dynamically based on filters applied during report interactions, providing aggregated results across rows.
Q. Which gives better performance: Calculated columns or measures?
Generally, measures provide better performance compared to calculated columns because they are computed at query time rather than during data load. Measures also reduce memory usage since they do not increase model size like calculated columns do.
Q. What are the different types of relationships in Power BI?
The different types of relationships include:
- One-to-One (1:1): Each record in one table corresponds to one record in another table.
- One-to-Many (1:N): One record from one table relates to multiple records in another table.
- Many-to-Many (N:N): Records from both tables can relate to multiple records from each other.
Q. How do you create relationships in Power BI?
Relationships can be created by navigating to the Model view in Power BI Desktop and dragging lines between fields that represent keys in related tables. Alternatively, users can define relationships through the "Manage Relationships" dialog box by specifying primary and foreign keys.
Q. Can you have a table in the model which does not have any relationship with other tables?
Yes, it is possible to have standalone tables without relationships with other tables; these tables can still be used within measures or calculations but won't interact with other tables' filters or context.
Q. What are the different types of joins in Power BI and their uses?
Power BI supports several join types:
- Inner Join: Returns only matching rows from both tables.
- Left Join: Returns all rows from the left table and matching rows from the right table; non-matching rows will have nulls.
- Right Join: Returns all rows from the right table with matching rows from the left; non-matching rows will have nulls.
- Full Outer Join: Returns all rows when there is a match in either left or right table records.
Q. What are the major differences between Power BI and Excel?
Key differences include:
- Data Visualization: Power BI offers advanced visualization options compared to Excel's basic charts.
- Data Capacity: Power BI handles larger datasets more efficiently than Excel's limitations.
- Collaboration: Power BI facilitates real-time collaboration through its cloud service while Excel primarily focuses on individual use unless integrated with SharePoint or similar tools.
Q. Explain the difference between Power BI Desktop and Power BI Service.
Power BI Desktop is a desktop application used for creating reports and dashboards offline, while Power BI Service is an online platform that enables sharing, collaboration, and real-time updates of reports created with Desktop. The Service also supports cloud storage options.
Q. What is a Power BI workspace?
A workspace in Power BI is a collaborative environment where users can create, manage, and share reports, dashboards, datasets, and other resources with team members or stakeholders within an organization.
Q. How do you optimize Power BI reports for performance?
To optimize reports for performance:
- Limit dataset size by removing unnecessary columns or rows.
- Use measures instead of calculated columns where possible.
- Minimize visuals on each report page to reduce rendering time.
- Implement query folding where applicable when using DirectQuery mode.
Q. What is the difference between a slicer and a filter in Power BI?
A slicer is a visual element that allows users to select values directly on reports for filtering data interactively; it provides an intuitive way to segment information visually. Filters apply more broadly at visual-level, page-level, or report-level without direct interaction through visuals.
Q. Explain the difference between SUM and SUMX in DAX.
SUM() calculates total values directly from a specified column across all rows without any additional context. In contrast, SUMX() evaluates an expression over a table row-by-row before summing up results; it's useful when calculations involve multiple columns or require context-specific evaluations.
Q. What is the purpose of time intelligence functions in Power BI?
Time intelligence functions allow users to perform calculations based on dates effectively—enabling comparisons over time periods such as year-to-date totals or previous year comparisons easily within DAX formulas.
Q. What is a Semantic Model?
A Semantic Model defines how data elements relate within databases or datasets while providing business logic through measures, hierarchies, metadata definitions etc., facilitating easier understanding and analysis by end-users without needing deep technical knowledge about underlying structures.