PL-300 Practice Exam 51 — 20 Questions

Question 1

A Power BI developer writes the Power Query M code shown in the exhibit. The code runs successfully but returns an error when the user selects a year from a slicer in the report. The error states: 'Expression.Error: The key did not match any rows in the table.' Which is the most likely cause?

Accepted Answer

The code hardcodes the year 2021, but the slicer passes a different year, causing the M code to fail when the source is queried. Option B is correct because the error 'The key did not match any rows in the table' occurs when a Power Query M query uses a hardcoded value (e.g., 2021) in a filter or lookup step, but the slicer passes a different year value to the report. When the slicer changes the parameter, the M code tries to retrieve data for that year, but the hardcoded key does not exist in the source table, causing the key lookup to fail. This is a classic parameterization issue where the M code should use a dynamic reference to the slicer value instead of a literal.

Answer

The table name Sales does not exist in the database

Answer

The ProductID column has duplicate values

Answer

The data type of the Year column is text instead of number

Question 2

A company wants to create a Power BI report that shows sales performance by region. The data contains a table 'Sales' with columns: Date, Amount, RegionID, and ProductID. They also have a 'Regions' table with RegionID and RegionName. They want to display a matrix visual with RegionName on rows and Year on columns, with the sum of Amount as values. However, the report displays only 'RegionID' instead of 'RegionName'. What is the most likely cause?

Accepted Answer

There is no active relationship between the Sales and Regions tables.. Option D is correct because if there is no active relationship between the Sales and Regions tables, Power BI cannot use the RegionName from the Regions table to filter or group the Sales data. Instead, it defaults to displaying the RegionID from the Sales table, which is the only related field available in the visual. An active relationship must exist between the two tables on the RegionID columns for RegionName to appear in the matrix.

Answer

The relationship is configured as many-to-many.

Answer

The relationship direction is set to Both.

Answer

The RegionID column in the Sales table is hidden.

Question 3

Which TWO are valid ways to create a calculated table in Power BI?

Accepted Answer

CALENDARAUTO(). Option D is correct because `CALENDARAUTO()` is a dedicated DAX function that automatically generates a single-column calculated table containing a contiguous range of dates based on the data model's date columns. This is a standard and valid method for creating a calculated table in Power BI, commonly used for time intelligence calculations.

Answer

VALUES(Customer[Country])

Answer

CALCULATE(SUM(Sales[Amount]), ALL(Sales))

Answer

FILTER(Products, Products[Color] = "Red")

Question 4

A Power BI report includes a slicer for 'Year' and a line chart showing monthly sales. The report designer wants to ensure that when a user selects a year in the slicer, the line chart shows only the months of that year, with month names on the x-axis sorted chronologically. Which TWO actions must be taken?

Accepted Answer

Mark the Date table as a date table in the model.. Option A is correct because marking the Date table as a date table ensures that Power BI recognizes the table as containing a contiguous date range, which is required for time intelligence functions and proper date-based filtering. When a slicer filters by Year, the line chart must respect the date relationship; without a marked date table, the filter may not propagate correctly to the month level, and the x-axis may not display months in chronological order.

Answer

Create a date hierarchy with Year and Month.

Answer

Set the slicer to 'Single select' mode.

Answer

Hide the Month column in the Date table.

Question 5

A company uses Row-Level Security (RLS) in Power BI. They want to ensure that when a manager views the report, they see data for their own region plus any region where a salesperson reports to them. Which RLS approach should you implement?

Accepted Answer

Use a DAX filter that references the USERPRINCIPALNAME() function. Option A is correct because Row-Level Security (RLS) in Power BI uses DAX filters that can dynamically evaluate the current user's identity via USERPRINCIPALNAME() or USERNAME(). By creating a DAX rule that checks whether the manager's UPN matches the region manager or if the salesperson's manager UPN equals the current user, you can enforce dynamic, hierarchical data access without hardcoding roles per manager.

Answer

Use Power BI App permissions to restrict data

Answer

Create a static role for each manager and assign users

Answer

Apply RLS at the visual level using bookmarks

Question 6

Which THREE of the following are best practices for designing Power BI reports for mobile devices?

Accepted Answer

Create a separate mobile layout for the report.. Option B is correct because Power BI allows you to create a dedicated mobile layout that is separate from the desktop report layout. This enables you to optimize the visual arrangement, size, and visibility of visuals specifically for smaller screens, ensuring a better user experience on mobile devices.

Answer

Include all pages from the desktop report in the mobile layout.

Answer

Use only responsive visuals that automatically resize.

Question 7

A Power BI report includes a bar chart showing total sales by product category. The report designer wants to add a trend line to the chart to show the overall sales trend over time. Which type of visual should be used instead?

Accepted Answer

Line chart. A line chart is the correct visual to show a trend over time because it plots data points connected by straight lines, making it easy to see the overall direction and pattern of total sales across a continuous time axis. Bar charts, including stacked variants, are designed for comparing discrete categories, not for displaying continuous trends.

Answer

Stacked bar chart

Answer

Scatter chart

Answer

Pie chart

Question 8

A Power BI report uses a measure that calculates Year-over-Year sales growth. Users report that the measure shows incorrect values for January 2024 when compared to January 2023. The data model contains a Date table with a continuous date range from January 1, 2020 to December 31, 2024. Which DAX function is most likely causing the issue?

Accepted Answer

SAMEPERIODLASTYEAR. SAMEPERIODLASTYEAR is the most likely cause of the issue because it returns a set of dates from the previous year that exactly matches the current period's date range. For January 2024, it will return January 1–31, 2023, but if the Date table does not have a full contiguous range (e.g., missing weekends or holidays), or if the measure relies on a different granularity, the comparison may produce incorrect values. The other functions shift dates differently or return entire periods, which can cause mismatches in Year-over-Year calculations.

Answer

PARALLELPERIOD

Answer

DATEADD

Answer

PREVIOUSYEAR

Question 9

Match each data connectivity mode to its description.

Question 10

You are reviewing a Power Query M script that imports sales data. The script filters orders from 2023, groups by CustomerID to sum SubTotal, sorts descending, and takes the top 10 customers. However, the query fails with an error. What is the most likely cause?

Accepted Answer

The column name 'SubTotal' is misspelled; the correct column name is 'Subtotal'.. Option C is correct because the error is most likely caused by a misspelled column name in the M script. Power Query is case-sensitive for column names, so 'SubTotal' does not match the actual column 'Subtotal', causing a runtime error when the script tries to reference the non-existent column.

Answer

The parameters in Sql.Database are reversed; the correct order is database name first, then server.

Answer

The Table.FirstN function is missing the second argument; it should be Table.FirstN(#"Sorted Rows", 10).

Answer

The #date function cannot be used with a datetime column; use DateTime.From instead.

Question 11

You need to create a calculated column that categorizes sales amounts into 'Low', 'Medium', and 'High' based on thresholds. Which DAX expression should you use?

Accepted Answer

SWITCH(TRUE(), Sales[Amount] < 100, "Low", Sales[Amount] < 500, "Medium", "High"). Option A is correct because it uses SWITCH(TRUE(), ...) to evaluate multiple conditions sequentially, returning the first matching result. This is the standard pattern for categorizing continuous values into discrete buckets in DAX, as SWITCH evaluates conditions in order and stops at the first TRUE condition.

Answer

IF(Sales[Amount] < 100, "Low", IF(Sales[Amount] < 500, "Medium", "High"))

Answer

SELECTEDVALUE(Sales[Amount]) & "Category"

Answer

SWITCH(Sales[Amount], 100, "Low", 500, "Medium", "High")

Question 12

Which THREE are data sources that can be imported into Power BI Desktop?

Accepted Answer

SQL Server database. A is correct because Power BI Desktop includes native connectors for SQL Server databases, allowing direct import of data via T-SQL queries or table selection. This is a first-class data source in the Get Data experience, supporting Windows and SQL Server authentication.

Answer

PDF file

Answer

Word document

Question 13

Which TWO actions can help reduce the size of a Power BI dataset when preparing data?

Accepted Answer

Aggregate transaction data to daily level. Aggregating transaction data to a daily level reduces the number of rows in the dataset, which directly decreases the storage footprint and improves refresh performance. Power BI compresses data more efficiently when cardinality is lower, and fewer rows mean smaller column dictionaries and reduced page compression overhead.

Answer

Include all historical data

Answer

Add calculated columns

Answer

Use DirectQuery mode

Question 14

You are preparing data for a Power BI report that analyzes customer churn. The source data contains the following columns: CustomerID, Churn (Yes/No), AgeGroup (Teen, Adult, Senior), SubscriptionType (Basic, Premium), MonthlyCharges, TotalCharges, TenureMonths. You need to ensure data quality and optimize the model. Which TWO actions should you take? (Choose two.)

Accepted Answer

Remove TotalCharges column if it can be calculated from MonthlyCharges and TenureMonths.. Option C is correct because removing derived columns like TotalCharges (which equals MonthlyCharges × TenureMonths) reduces data redundancy, improves model size, and avoids potential inconsistencies. Option D is correct because setting CustomerID as a unique key and marking it as the primary column ensures proper row-level identity, enables efficient relationships, and is a best practice for star schema modeling in Power BI.

Answer

Convert Churn column to a numeric 0/1 column.

Answer

Create a calculated column for AverageCharges per customer.

Answer

Create a separate table for subscription types.

Question 15

You are modeling data from an Azure SQL Database into Power BI. The source table 'Sales' contains 10 million rows. You need to ensure that the data model supports fast query performance for a report that shows sales by month and product category. The report uses a slicer for year. What is the best practice for improving performance?

Accepted Answer

Create an aggregate table in Power BI that pre-aggregates sales by month and product category.. Option D is correct because creating an aggregate table in Power BI that pre-aggregates sales by month and product category drastically reduces the number of rows the report must scan, from 10 million to a much smaller set of aggregated rows. This enables fast query performance for the slicer and visual-level filters, as Power BI can leverage the aggregate table via its aggregation feature, which automatically redirects queries to the pre-summarized data when possible.

Answer

Disable the auto-date/time feature.

Answer

Increase the data load frequency to every 15 minutes.

Answer

Use DirectQuery mode to query the source database directly.

Question 16

You have a Power BI dataset that is refreshed every hour from an on-premises data source using an enterprise gateway. The refresh consistently fails at 2:00 AM. What is the most likely cause?

Accepted Answer

The on-premises data gateway is scheduled to reboot at 2:00 AM.. The consistent failure at exactly 2:00 AM strongly points to a scheduled event on the on-premises data gateway, such as a reboot or maintenance window. Enterprise gateways can be configured to reboot periodically for updates or health reasons, and if this coincides with the refresh schedule, the gateway will be unavailable, causing the refresh to fail. Transient errors or cloud maintenance would not produce a perfectly consistent daily failure at the same time.

Answer

The refresh is failing due to a transient network error.

Answer

The data source is undergoing maintenance in the cloud.

Answer

The scheduled refresh time conflicts with another refresh.

Question 17

You are reviewing a Power Query query that combines data from multiple CSV files in a folder. The query uses the 'Combine Files' function. Which TWO actions can you take to improve the performance of this query?

Accepted Answer

Disable the 'Promote Headers' step if the headers are not needed.. Option B is correct because disabling the 'Promote Headers' step reduces the number of transformations applied to each file during the combine operation. When headers are not needed, skipping this step avoids an extra row promotion and type detection pass, which can significantly reduce query execution time, especially when combining many files.

Answer

Load all data to the data model without filtering.

Answer

Increase the scheduled refresh frequency.

Answer

Enable 'Fast Combine' in the Power Query options.

Question 18

Which TWO of the following are valid DAX functions for time intelligence?

Accepted Answer

TOTALYTD. TOTALYTD is a valid DAX time intelligence function that calculates the year-to-date value of an expression, typically used with a date column to aggregate data from the start of the year to the current context. It requires a properly marked date table with continuous dates to function correctly.

Answer

RANKX

Answer

SUM

Answer

CALCULATE

Question 19

You are preparing data for a report that requires joining sales data from a SQL database with customer demographic data from a CSV file. The CSV file contains duplicate customer IDs. How should you handle duplicates to ensure accurate analysis?

Accepted Answer

In Power Query, remove duplicates from the CustomerID column in the CSV table before merging.. Option D is correct because removing duplicates from the CustomerID column in the CSV table before merging ensures a one-to-one or one-to-many relationship with the SQL sales data, preventing inflated row counts and inaccurate aggregations. In Power Query, the 'Remove Duplicates' operation keeps the first occurrence by default, which is appropriate when no other filtering criteria are specified. This step is critical for maintaining referential integrity in the data model.

Answer

Group by CustomerID and aggregate all columns.

Answer

In Power Query, use 'Merge Queries' and select 'Merge with duplicates' option.

Answer

Load both tables as-is and create a relationship in the data model.

Question 20

You receive a Power Query error: 'Expression.Error: The key didn't match any rows in the table.' This occurs when merging two queries. What is the most likely cause?

Accepted Answer

The join column in the first table contains values that do not exist in the second table.. Option D is correct because the error 'The key didn't match any rows in the table' occurs during a merge operation when Power Query attempts to find a matching value from the first table's join column in the second table's join column, but no match exists. This is a standard behavior for inner joins or left outer joins where the lookup fails, and it typically indicates that the first table contains values absent in the second table.

Answer

The join columns have different data types.

Answer

The second table is empty due to a permission issue.

Answer

The join columns contain duplicate values.

PL-300 Practice Exam 51 — 20 Questions

Exhibit

PL-300 Practice Exam 51 — 20 Questions

Exhibit