Top 30 Power BI Interview Questions and Answers
Top 30 Power BI Interview Questions and Answers
The limitations of Managed Enterprise BI led to the birth of Self-service BI. There are significant differences that separate them.
|Managed Enterprise BI||Self-service BI|
|In Managed Enterprise BI, data flowed in from a plethora of data sources and, for this reason, there was no order in which companies ingested and managed their data sources.||Self-service BI enabled companies to ingest data from any data source, seamlessly. Companies could take in data from any source and in any format, as well.|
|Companies were failing to conduct their business operations, effectively, as they were not able to report and analyze data, and collaborate for collecting valuable insights from it.||With data ingestion falling into order, companies were able to process data and, consequently, conduct business operations with ease.|
|There were time constraints and lack of proper information when it came to analyzing data.||Analyzing data became easy, and the Self-service BI software did that implicitly. Time constraints were hence alleviated.|
|Third-party vendors were employed to help companies make the most out of their data sources. This was leading to budget problems and slow productivity.||There was no need of third-party vendors anymore and, therefore, all associated constraints were eradicated.|
|Complex programming skills were necessary for generating reports.||Users could generate intuitive and actionable dashboards almost instantaneously without executing complex programming codes.|
Self-service BI or Self-service Business Intelligence (SSBI) is an approach to data analytics, reporting, and visualization that enables users to generate easy-to-understand, intuitive, and actionable dashboards, almost instantaneously. The most striking feature of SSBI is the fact that users are not required to be adept at technical expertise when it comes to data reporting. Using available filters and data manipulation options, they can influence data as per their business needs and further create reports. There are two parts to Microsoft SSBI:
- Excel BI toolkit
- Power BI
A cloud-based data reporting and visualization tool, Power BI makes it possible for users to generate reports online. Once reports are generated, users can share them with their colleagues in their workplace. This aspect of Power BI makes it quite popular among business users. And therefore, Power BI is both an interesting and promising career option.
Features of Power BI are many. The most notable ones are:
- It allows users to transform data into visuals and share those visuals with colleagues.
- It allows users to explore and analyze data from all sources (in an all-in-one view).
- It allows users to scale across organizations with built-in governance and security.
- Once an output is generated, users can display the same in multiple devices that are compatible with the Power BI application.
- With Power BI natural language processing or Power BI Q&A, users can perform queries on reports using simple English words.
Well, users can use Power BI for free. However, the best of Power BI can be availed with the Power BI Pro subscription account. This can be purchased from the Microsoft Store. The subscription account basically offers an enhanced version of several features that are available with the Power BI free account. Most business users use a subscribed account as it offers more data refreshes per day and other features as compared to the free version.
Power BI brings in a lot of flexibility when it comes to data reporting and visualization. For this reason, the complete Power BI package has been divided into three versions. These versions allow all kinds of users to leverage the functionalities of Power BI to the fullest.
The versions are:
- Power BI Desktop: The on-premise version for Windows 10
- Power BI Service: For publishing to the cloud
- Mobile Power BI: For mobile users
Power BI Desktop is a Windows desktop-based application for personal computers, primarily for designing, generating, and publishing reports to the cloud. Used as an on-premise version of Power BI, Power BI Desktop can run on PCs and work full-fledged even when the system is not connected to the Internet. Just when users want to publish their reports to the cloud or share with colleagues, they are supposed to connect to the Internet. Power BI Desktop is basically the first application that users jump into when they board on Power BI.
There are five different components of Power BI.
- Power Pivot: The data transformation engine that fetches and cleans data and loads on to Power Query
- Power Query: The data transformation engine that operates the loaded data
- Power Q&A: Makes it possible for users to interact with reports using simple English language
- Power View: A data visualization technology lets users create interactive charts, graphs, maps, and other visuals
- Power Map: Enables the processing of accurate geographic locations in data sets.
When users click on the Get Data icon in Power BI, a drop-down menu appears and it shows all data sources from which data can be ingested. Data can actually be directly ingested from any source including files in Excel, CSV, XML, JSON, PDF, and SharePoint folder formats and databases such as SQL, Access, SQL Server Analysis Services, Oracle, IBM, MySQL, and much more. Also, Power BI data sets and Power BI dataflows are compatible. Data can also be taken in from Azure and other online sources.
Data can be filtered using filters that are available in Power BI, implicitly. There are basically three types of filters, namely, Page-level filters, Drillthrough filters, and Report-level filters.
- Drillthrough Filters: With drillthrough in Power BI Desktop, users can create a page in their reports that focuses on specific entities such as suppliers, customers, or manufacturers.
- Page-level Filters: These are used to filter charts that are present in individual pages.
- Report-level Filters: They are used to simultaneously filter charts that are present in all pages of a report.
When data is ingested into Power BI, it is basically stored in Fact and Dimension Tables.
- Fact Tables: The central table in a start schema of a data warehouse, a fact table stores quantitative information for analysis and is not normalized in most cases.
- Dimension Tables: It is just another table in the star schema that is used to store attributes and dimensions that describe objects that are stored in a fact table.
Content packs are packaged reports, dashboards, and data sets, which can be shared with other Power BI users in your organization. When a content pack is connected on the Powerbi.com portal, report items are merged into workspace lists.
The most notable features of content packs are as follows:
- Provide access to specific groups or entire organizations
- Can be customized with a title and a description to help users select the right pack
- Users who have access to the content pack can create new dashboards from the contents
There are three different views in Power BI, each of which serves a different purpose.
- Report View: Users can add visualizations and additional report pages and publish the same on the portal from here.
- Data View: Data shaping can be performed through Query Editor tools.
- Relationship View: Users can manage relationships between data sets in this view.
Row-level security restricts the data that a user can view and has access to, based on filters. For configuring row-level security, users can define rules and roles within Power BI Desktop and publish the same to Power BI Service. Also, the username() function can be used alongside table relationships to restrict data to the current user.
However, for enabling row-level security, a Power BI Pro subscription account is required, and Excel sheets can only be used when they are converted to the .pbix file format.
DAX or Data Analysis Expressions can be used to query and return data by a table expression. It is a formula language which is used to perform basic calculations and data analysis on data in Power Pivot. Also, it is used to compute calculated columns, calculated fields, and measures. However, data cannot be inserted or modified using DAX.
Total Sales = SUM(Sales[SalesAmount])
Where, Total Sales is a ‘Measure’; SUM is a ‘DAX Function’; and Sales[SalesAmount] represents the referenced table and referenced column name.
Benefits of using variables in DAX:
- Variables can be reused in DAX queries, thus avoiding additional queries of source database.
- Variables make DAX expressions understandable.
Bidirectional cross-filtering in Power BI Desktop allows data modelers to determine how they want filters to flow for data using relationships between tables. With bidirectional cross-filtering, the filter context is propagated to a second related table on the other side of a table relationship. This can help them solve the many-to-many problem without writing complicated DAX formulas. Thus, bidirectional cross-filtering simplifies the job for data modelers.
If there are no null values or duplicate rows, relationships between tables can be defined in two ways:
- Manually: Users can manually define relationships between tables using primary and foreign keys.
- With the Autodetect feature: When enabled, this inherent feature of Power BI detects relationships between tables and creates them automatically.
By using Power BI Query Editor, users can load data from a wider number of data sources and apply transformations on them, including adding new columns and measures.
Power BI Query Editor comprises four tabs:
|Query Editor Tab||Use Case|
Advanced Editor can be used to see the query that Power BI runs against data sources to import data.
- The query is written in M-code, the Power Query Formula Language
- To view the query code from Power BI Desktop, choose Edit Queries from the Home tab
- From either the Home or the View tab, click on Advanced Editor to work on that query
- The Advanced Editor window opens, displaying the code for the currently selected query
- When you make transformations to your data in Query Editor, the steps are saved to the Applied Steps in the Query Settings
- These steps are also applied to the code in the Advanced Editor
By formatting data, users can help Power BI categorize and identify data, making it much easier to work with.
- You enter a custom formula to create a new column, including calculations using values from other columns
- To create a new column, click on Add Custom Column
- In the new column name box, type the name of the column and add your formula to the custom column formula box; for example, [ShipDate] – [OrderDate]
- Select a column from the available columns list and click on Insert or double-click to add it to the custom column formula text box. Then, click on OK
- The new column is appended to the table, and the formula is visible in the Formula Bar
Custom Column Formula
= Table.AddColumn(#"Sorted Rows", "DaysOrderToShip", each [ShipDate] - [OrderDate])
The above code is the formula to create a custom column, which calculates the days from when an order was placed to when it got shipped.
The most common data shaping techniques are:
- Removing Columns and Rows
- Adding Indexes
- Applying a Sort Order
|Calculated Columns||Calculated Tables||Measures|
The primary in-memory analytics engine behind Power Pivot is xVelocity. This engine handles large amount of data as it stores data in columnar databases. In in-memory analytics, all data is loaded to RAM memory, and therefore processing speed is really fast.
A powerful and flexible new tool under Power BI umbrella, Power BI Designer empowers users to create intuitive reports and dashboards, easily and quickly, and also lets users change visual views of their data at fingertips for better analytics and informed decision-making. This designer is a host of drag-and-drop capabilities that help users place content exactly where they want it on the report canvas in a well-structured layout.
Yes, it is possible. Gateways can be used to do so.
- For SharePoint: Data Management Gateway
- For Powerbi.com: Power BI Personal Gateway
A gateway basically acts as a bridge between on-premise data sources and Azure Cloud Services.
Personal Gateway: Data can be imported and valid on Power BI Service only. Also, this gateway can only be used by one person.
On-premises Gateway: This gateway is the advanced form of Personal gateway. It supports Direct Query, and multiple users can use this for refreshing data.
Through map chart and filled map chart, Power BI makes it possible for users to visually map geographic data, both globally and regionally.
- Power BI integrates with Bing Maps to find default coordinates for locations in a process known as geocoding.
- This integration means that users do not need to provide longitude and latitude coordinates.
When you do that, data gets selected and copied to the clipboard. Further, the copied data can be pasted anywhere as per the requirement of the user.
Z-order is a design strategy which is used for arranging visuals over shapes. Also, z-order can be defined as an implementation method which can be applied when reports have multiple elements. Further, this can also be used to refresh the display after the order of items in a report is changed.
There is only one prerequisite for this. Before connecting to a database in Azure SQL Database, users should configure firewall settings to allow remote connections.