Power BI Mock Interview No.3 | Power BI Interview | Power BI Live Interview |

Summary

This interview transcript delves into the intricacies of Power BI, covering topics such as calculated columns versus measures, data visualization techniques, and the use of DAX functions. It explores the impact of certain features on report performance and file size, discusses the utility of buttons and tooltips in enhancing user interaction, and touches on advanced concepts like cross-report drill-through and data alerts. The interviewee demonstrates a solid grasp of Power BI's capabilities, reflecting on their experience with various features and functions, including AI-based visuals and the latest updates to the platform.

Takeaways

• 😀 The difference between calculated columns and measures is that calculated columns work on row context and do not contain aggregation functions, while measures work on filter context and must contain aggregation functions.
• 😀 Calculated columns increase file size in reports, and they change the schema by adding new columns.
• 😀 Distinct function removes duplicate rows, whereas the Value function counts blank values.
• 😀 Calendar function returns a table with a single date column, and additional date columns can be added using functions.
• 😀 Stacked bar charts show the composition of variables, while 100% stacked bar charts show the relative percentage of multiple data sets.
• 😀 The ALL function in DAX returns all rows in a table, ignoring any filters that might have been applied.
• 😀 ALLSELECTED and ALLEXCEPT functions in DAX return all rows in a table, ignoring internal filters but keeping filters from outside sources.
• 😀 The 'What If' parameter in Power BI is used for visualization and analyzing the effect of changing variables on output.
• 😀 Buttons in Power BI can be used to create interactive reports that behave similarly to apps.
• 😀 Data alerts in Power BI are used to track and monitor important changes in business data, and they can be set up in the settings.

Q & A

What is the difference between a calculated column and a measure in Power BI?

A calculated column operates on a row-by-row basis and does not contain any aggregation functions, whereas a measure works on an aggregated level, often involving aggregation functions like SUM or COUNT. Calculated columns increase file size as they are stored in memory, while measures consume CPU during calculation.

How does the 'ALL' function in DAX affect the row context?

The 'ALL' function in DAX removes all filters from the table, returning all rows without any applied filters. This can be useful when you need to access all data without any restrictions.

What is the primary purpose of using 'ALLSELECTED' and 'ALLEXCEPT' functions in DAX?

The 'ALLSELECTED' function returns all rows in a table ignoring any internal filters but keeping any external filters applied. 'ALLEXCEPT', on the other hand, removes all filters except for those specified in the function, allowing for more granular control over the data being analyzed.

How does the 'DISTINCT' function differ from the 'VALUES' function in DAX?

The 'DISTINCT' function removes duplicate rows and returns only unique rows from a table, whereas the 'VALUES' function includes all rows, including duplicates, and also counts blank values.

What is the main advantage of using a 100% stacked bar chart over a regular stacked bar chart?

A 100% stacked bar chart is more effective for showing the relative percentage of multiple data sets, making it easier for clients to understand the proportion of each variable, regardless of their technical knowledge.

Can you explain the concept of 'What-If' parameters in Power BI?

What-If parameters in Power BI are used to visualize and analyze the effect of changing variables on the output. They allow users to input different values and immediately see how the report results are affected, which is useful for sensitivity analysis.

How can buttons in Power BI enhance the interactivity of a report?

Buttons in Power BI can make a report behave similarly to an app, allowing users to interact with the report through clicks and actions. They can be used to filter data, navigate between pages, or trigger specific visualizations.

What is the purpose of using tooltips in Power BI visuals?

Tooltips provide brief, informative messages when the user hovers over a visual element, offering quick insights and additional context about the data being presented without cluttering the main view.

What are some common DAX functions used to manipulate table data in Power BI?

Common DAX functions for table manipulation include 'ADDCOLUMNS', 'CROSSJOIN', 'GROUPBY', and 'UNION'. These functions allow for adding new columns, combining data from multiple tables, grouping data for aggregation, and merging tables respectively.

How does the 'CALCULATE' function in DAX differ from other aggregate functions?

The 'CALCULATE' function in DAX is unique because it allows for conditional aggregation. It can be used with filter arguments to perform calculations only on a subset of the data that meets certain conditions.

Can you describe the scenario where 'CROSS REPORT DRILL THROUGH' would be useful?

Cross report drill through is useful when you want to create a link between two different reports, allowing users to drill down from one report to another. This is particularly useful for detailed analysis where additional context or data is available in a separate report.