This article was published as a part of the Data Science Blogathon.
Power BI is one of the most popular data visualization and analytics software product developed by Microsoft. Power BI interviews will provide insights from a variety of data by modeling data and telling stories from data visualizations using reports and dashboards.
Therefore, it becomes very necessary for every aspiring Data A good knowledge about Power BI.
In this article, we will discuss some important Power BI interview questions which will help you to get a good understanding of Power BI techniques.
Interview Questions for Power BI
1. What is Power BI?
Power BI is a data visualization tool developed by Microsoft that helps to extract meaningful information from the raw data by visualizing data sets from multiple sources like Excel, SAP, etc. Using Power BI, we can share the data insights with anyone by sharing Power BI reports.
2. What are the building blocks of Power BI?
Below are the five building blocks of Power BI:
1. Visualizations: A visualization is visual like tables, column charts, scatter charts, maps, etc. which can be used to represent your data visually.
2. Datasets: A dataset is a collection of data that can be used by Power BI for creating visuals. Dataset is a combination of many data sources like Web, Dataverse, CSV, etc.
3. Reports: Reports are a collection of visualizations that appear together on a page. The report can be developed either using Power BI Desktop or Power BI Service. A report may contain more than a page.
4. Dashboards: Dashboards are single-page presentations having one or more visualizations added to them. For example, Example: Sales dashboard can have pie charts, KPI scorecards, bar charts, maps, etc.
5. Tiles: A tile is a rectangular box that holds visuals like cards, pie charts, etc.
3. What is Power Query?
Power Query is a data preparation and data transformation engine used to perform ETL processing. Using power query, we can change the data type of columns, pivot and unpivot columns, summarize and group rows, join and append data, etc. Thus, a power query helps to perform data transformation, data cleaning, change the shape of data, etc.
4. Explain query folding in power query?
Query folding is the capability of Power Query in which the steps defined in the Query editor generate a single query statement to retrieve and transform source data. Query folding improves query processing performance.
5. What are the different dataset connectivity modes in Power BI?
The below three dataset connectivity modes are available in Power BI:
1. Import mode: Import mode is the default dataset connectivity mode in Power BI as it delivers fast performance.
Imported data is always stored in the disk and during the querying or data refreshing process, the data must be fully loaded.
2. Direct Query Mode: Direct Query mode doesn’t import data but it directly retrieves data from underlying data sources using native queries. This mode is used when the data volumes are very large and data is nearly real-time.
3. Composite Mode: Composite mode could integrate various Direct Query data sources or can combine datasets imported by Import and Direct Query modes. It gives the best performance.
6. What are filters in Power BI Reports?
Filters are used to filter data. Filters can be applied at a visual level, page level, or report level. Apart, from this Drillthrough filters can be used to drill through from one page of a report to another. Below are the different types of filters available in Power BI:
- URL filters–transient
- Pass-Through filters
- Drill-down filters
- Cross Drill filters
- Include/Exclude filters
- Manual filters
- Auto filters
- Drillthrough filters (Invokes Drillthrough)
- Drillthrough filters (Transient)
7. What is the difference between dashboard and report in Power BI?
|A dashboard contains only one page.||Reports may contain one or more pages.|
|Alerts for the dashboard can be set.||The option to set an alert on the report is not available.|
|Dashboards can only be developed in Power BI Service.||Reports can be developed either on a Power BI Desktop or Power BI service.|
|Drilling down in visuals is possible only if the user has pinned an entire report page to a dashboard.||Drilling down in visuals is possible in reports.|
8. What is DAX and what are some commonly used DAX functions in Power BI?
Data Analysis Expressions (DAX) is a formula language used for building formulas in Analysis Services, Power BI, and Power Pivot in Excel data models. DAX contains a variety of functions like filter functions, logical functions, aggregation functions, etc. DAX is used to calculate the results of calculated columns and measures in Power BI. Below are the some commonly used DAX functions in Power BI:
- MIN, MAX, COUNTROWS, DISTINCTCOUNT, SUM, AVG
- SWITCH, OR, AND, IF
- ISFILTERED, ISCROSSFILTERED, ISBLANK
- CALCULATE, FILTER, VALUES, AND ALL
- ISEMPTY, SUMMARIZECOLUMNS, UNION, INTERSECT, EXCEPT, NATURALINNERJOIN, NATURALLEFTEROUTERJOIN
- VAR (Variables)
9. What is Get data in Power BI?
Get data option is available in the Home tab on the Power BI desktop. Get data is used to connect to different data sources for loading data for visualization and analysis. You can load the data first or perform a data transformation before loading it. Users can import data from Excel, Text/CSV, Web, Dataverse, Oracle, MySQL, Snowflake, SAP databases, Google BigQuery, MariaDB, Azure SQL, etc. in Power BI.
10. What is the difference between the calculated column and measure in Power BI?
|Values in the calculated column are calculated when the report is refreshed.||Values of measure are calculated on the fly.|
|Calculated column consumes memory, ie, values are stored in memory.||Measures consume CPU, ie, values are not stored anywhere.|
|A calculated column is mainly used for row by row calculation.||Measures are mainly used for saving results of aggregation.|
In this article, we have seen some of the important questions that can be asked in Power BI interviews. However, it’s recommended apart from these Power BI interview questions, you also practice developing reports and develop an understanding of data transformation and SQL. To summarize, the following were the major takeaways from the above Power BI interview questions:
- We learned about what is Power BI and what are building blocks of Power BI
- We understand how we can get data in Power BI and the different modes of dataset connectivity available in Power BI.
- We have seen how dashboards and reports are different from each other.
- We got an understanding of how we can use filters in Power BI.
- Apart from this, we saw what is power query, DAX functions, and how to use DAX functions.
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