Power BI Interview Questions

 

1. How would you define Power BI as an effective solution?

Power BI is a strong business analytical tool that creates useful insights and reports by collating data from unrelated sources. This data can be extracted from any source like Microsoft Excel or hybrid data warehouses. Power BI drives an extreme level of utility and purpose using interactive graphical interface and visualizations. You can create reports using the Excel BI toolkit and share them on-cloud with your colleagues.

2). What is self-service business intelligence?

Ans: Self-Service Business Intelligence (SSBI)

• SSBI is an approach to data analytics that enables business users to filter, segment, and, analyze their data, without the in-depth technical knowledge in statistical analysis, business intelligence (BI).
• SSBI has made it easier for end users to access their data and create various visuals to get better business insights.
• Anybody who has a basic understanding of the data can create reports to build intuitive and shareable dashboards.

3). What is Power BI?

Ans: Power BI is a cloud-based data sharing environment. Once you have developed reports using Power Query, Power Pivot and Power View, you can share your insights with your colleagues. This is where Power BI enters the equation. Power BI, which technically is an aspect of SharePoint online, lets you load Excel workbooks into the cloud and share them with a chosen group of co-workers. Not only that, but your colleagues can interact with your reports to apply filters and slicers to highlight data. They are completed by Power BI, a simple way of sharing your analysis and insights from the Microsoft cloud. know more at Power bi online training

Power BI features allow you to:

• Share presentations and queries with your colleagues.
• Update your Excel file from data sources that can be on-site or in the cloud.
• Display the output on multiple devices. This includes PCs, tablets, and HTML 5-enabled mobile devices that use the Power BI app.
• Query your data using natural language processing (or Q&A, as it is known).

4). What is Power BI Desktop?

Ans: Power BI Desktop is a free desktop application that can be installed right on your own computer. Power BI Desktop works cohesively with the Power BI service by providing advanced data exploration, shaping, modeling, and creating report with highly interactive visualizations. You can save your work to a file or publish your data and reports right to your Power BI site to share with others.

5). What data sources can Power BI connect to?

Ans: The list of data sources for Power BI is extensive, but it can be grouped into the following:

• Files: Data can be imported from Excel (.xlsx, xlxm), Power BI Desktop files (.pbix) and Comma Separated Value (.csv).
• Content Packs: It is a collection of related documents or files that are stored as a group. In Power BI, there are two types of content packs, firstly those from services providers like Google Analytics, Marketo or Salesforce and secondly those created and shared by other users in your organization.
• Connectors to databases and other datasets such as Azure SQL, Databaseand SQL, Server Analysis Services tabular data, etc.

6). What are Building Blocks in Power BI?

Ans: The following are the Building Blocks (or) key components of Power BI:

1. Visualizations: Visualization is a visual representation of data.
   Example: Pie Chart, Line Graph, Side by Side Bar Charts, Graphical Presentation of the source data on top of Geographical Map, Tree Map, etc.
   
2. Datasets: Dataset is a collection of data that Power BI uses to create its visualizations.
   Example: Excel sheets, Oracle or SQL server tables.
   
3. Reports: Report is a collection of visualizations that appear together on one or more pages.
   Example: Sales by Country, State, City Report, Logistic Performance report, Profit by Products report etc.
   
4. Dashboards: Dashboard is single layer presentation of multiple visualizations, i.e we can integrate one or more visualizations into one page layer.
   Example: Sales dashboard can have pie charts, geographical maps and bar charts.
   
5. Tiles: Tile is a single visualization in a report or on a dashboard.
   Example: Pie Chart in Dashboard or Report.

7). What are the different types of filters in Power BI Reports?

Ans: Power BI provides variety of option to filter report, data and visualization. The following are the list of Filter types.

• Visual-level Filters: These filters work on only an individual visualization, reducing the amount of data that the visualization can see. Moreover, visual-level filters can filter both data and calculations.
• Page-level Filters: These filters work at the report-page level. Different pages in the same report can have different page-level filters.
• Report-level Filters: There filters work on the entire report, filtering all pages and visualizations included in the report.

We know that Power BI visual have interactions feature, which makes filtering a report a breeze. Visual interactions are useful, but they come with some limitations:

• The filter is not saved as part of the report. Whenever you open a report, you can begin to play with visual filters but there is no way to store the filter in the saved report.
• The filter is always visible. Sometimes you want a filter for the entire report, but you do not want any visual indication of the filter being applied. know more at Power bi training

8). What are content packs in Power BI?

Ans: Content packs for services are pre-built solutions for popular services as part of the Power BI experience. A subscriber to a supported service, can quickly connect to their account from Power BI to see their data through live dashboards and interactive reports that have been pre-built for them. Microsoft has released content packs for popular services such as Salesforce.com, Marketo, Adobe Analytics, Azure Mobile Engagement, CircuitID, comScore Digital Analytix, Quickbooks Online, SQL Sentry and tyGraph. 

Organizational content packs provide users, BI professionals, and system integrator the tools to build their own content packs to share purpose-built dashboards, reports, and datasets within their organization.

Power BI Interview Questions – DAX

9). What is DAX?

Ans: To do basic calculation and data analysis on data in power pivot, we use Data Analysis Expression (DAX). It is formula language used to compute calculated column and calculated field.

• DAX works on column values.
• DAX can not modify or insert data.
• We can create calculated column and measures with DAX  but we can not calculate rows using DAX.

• 10). What are the most common DAX Functions used?
  

  Ans: Below are some of the most commonly used DAX function: 

  • SUM, MIN, MAX, AVG, COUNTROWS, DISTINCTCOUNT
  • IF, AND, OR, SWITCH
  • ISBLANK, ISFILTERED, ISCROSSFILTERED
  • VALUES, ALL, FILTER, CALCULATE,
  • UNION, INTERSECT, EXCEPT, NATURALINNERJOIN, NATURALLEFTEROUTERJOIN,
    SUMMARIZECOLUMNS, ISEMPTY,
  • VAR (Variables)
  • GEOMEAN, MEDIAN, DATEDIFF

  11). How is the FILTER function used?
  

  Ans: The FILTER function returns a table with a filter condition applied for each of its source table rows. The FILTER function is rarely used in isolation, it’s generally used as a parameter to other functions such as CALCULATE. 

  • FILTER is an iterator and thus can negatively impact performance over large source tables.
  • Complex filtering logic can be applied such as referencing a measure in a filter expression.
    • FILTER(MyTable,[SalesMetric] > 500)

  12). What is special or unique about the CALCULATE and CALCULATETABLE functions?
  

  Ans: These are the only functions that allow you modify filter context of measures or tables.

• • Add to existing filter context of queries.
  • Override filter context from queries.
  • Remove existing filter context from queries.

  Limitations:

  • Filter parameters can only operate on a single column at a time.
  • Filter parameters cannot reference a metric.

  13). What is the common table function for grouping data?
  

  Ans:  SUMMARIZE()

  • Main groupby function in SSAS.
  • Recommended practice is to specify table and group by columns but not metrics.You can use ADDCOLUMNS function.

   SUMMARIZECOLUMNS

  • New group by function for SSAS and Power BI Desktop; more efficient.
  • Specify group by columns, table, and expressions.

  14). What are some benefits of using Variables in DAX ?
  

  Ans: Below are some of the benefits: 

  • By declaring and evaluating a variable, the variable can be reused multiple times in a DAX expression, thus avoiding additional queries of the source database.
  • Variables can make DAX expressions more intuitive/logical to interpret.
  • Variables are only scoped to their measure or query, they cannot be shared among measures, queries or be defined at the model level.

  15). How would you create trailing X month metrics via DAX against a non-standard calendar?
  

  Ans:  The  solution will involve:

  1. CALCULATE function to control (take over) filter context of measures.
  2. ALL to remove existing filters on the date dimension.
  3. FILTER to identify which rows of the date dimension to use.

  Alternatively, CONTAINS may be used:

  • CALCULATE(FILTER(ALL(‘DATE’),…….))
    

  16). What are the different Excel BI add-in?

  Ans: Below are the most important BI add-in to Excel:

  • Power Query: It helps in finding, editing and loading external data.
  • Power Pivot: Its mainly used for data modeling and analysis.

  • Power View: It is used to design visual and interactively reports.
  • Power Map: It helps to display insights on 3D Map.

  Power BI Interview Questions – Power Pivot

  17). What is Power Pivot?

  Ans: Power Pivot is an add-in for Microsoft Excel 2010 that enables you to import millions of rows of data from multiple data sources into a single Excel workbook. It lets you create relationships between heterogeneous data, create calculated columns and measures using formulas, build PivotTables and PivotCharts. You can then further analyze the data so that you can make timely business decisions without requiring IT assistance. know more at Power bi online course

  18). What is Power Pivot Data Model?

  Ans: It is a model that is made up of data types, tables, columns, and table relations. These data tables are typically constructed for holding data for a business entity.

  19). What is xVelocity in-memory analytics engine used in Power Pivot?

  Ans: The main engine behind power pivot is the xVelocity in-memory analytics engine. It can handle large amount of data because it stores data in columnar databases, and in memory analytics which results in faster processing of data as it loads all data to RAM memory.

  21). What are some of differences in data modeling between Power BI Desktop and Power Pivot for Excel?

  Ans: Here are some of the differences:

  • Power BI Desktop supports bi-directional cross filtering relationships, security, calculated tables, and Direct Query options.
  • Power Pivot for Excel has single direction (one to many) relationships, calculated columns only, and supports import mode only. Security roles cannot be defined in Power Pivot for Excel.

  22). Can we have more than one active relationship between two tables in data model of power pivot?

  Ans: No, we cannot have more than one active relationship between two tables. However, can have more than one relationship between two tables but there will be only one active relationship and many inactive relationship. The dotted lines are inactive and continuous line are active.

  Power BI Interview Questions – Power Query

  23). What is Power Query?

  Ans: Power query is a ETL Tool used to shape, clean and transform data using intuitive interfaces without having to use coding. It helps the user to:

  • Import Data from wide range of sources from files, databases, big data, social media data, etc.
  • Join and append data from multiple data sources. 
    • Shape data as per requirement by removing and adding data.

  24). What are the data destinations for Power Queries?

  Ans: There are two destinations for output we get from power query:

  1. Load to a table in a worksheet.
  2. Load to the Excel Data Model.

  25). What is query folding in Power Query?

  Ans: Query folding is when steps defined in Power Query/Query Editor are translated into SQL and executed by the source database rather than the client machine. It’s important for processing performance and scalability, given limited resources on the client machine. know more at Power bi training course

  26). What are some common Power Query/Editor Transforms?
  

  Ans: Changing Data Types, Filtering Rows, Choosing/Removing Columns, Grouping, Splitting a column into multiple columns, Adding new Columns ,etc.