PL-300 Practice Test 9 — 10 Questions

Question 1

You are preparing data in Power BI Desktop. You have a table with a column 'CustomerID' that contains duplicate values. You need to create a relationship to another table that also has 'CustomerID'. However, the relationship requires unique values in at least one of the tables. What should you do?

Choose an answer to begin — your selection is scored in the full session.

Accepted Answer

Remove duplicate rows from the 'CustomerID' column in the dimension table.. To create a relationship in Power BI, at least one table must have unique values in the column used for the relationship. By removing duplicate rows from the 'CustomerID' column in the dimension table (which should contain unique identifiers), you ensure that the dimension table has unique values, allowing a one-to-many relationship to be established with the fact table. This is a standard data modeling practice in Power BI to enforce referential integrity.

Answer

Create a composite key using multiple columns.

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Use the 'Merge Queries' feature to combine the tables into one.

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Change the data type of 'CustomerID' to text.

Question 2

You manage a Power BI deployment that uses deployment pipelines. After promoting content from Development to Test, you notice that the Test workspace dataset uses a different data source than expected. What is the most likely reason?

Accepted Answer

The dataset parameters were not configured in the deployment pipeline rules.. Deployment pipeline rules allow you to configure dataset parameters (such as data source paths) to differ between pipeline stages. If these rules are not set, the dataset retains the data source configuration from the source stage (Development), causing the Test workspace to use an unexpected data source. The pipeline deploys the dataset artifact, but without parameter overrides, the data source connection string remains unchanged.

Answer

The pipeline didn't deploy the dataset because it was already in Test.

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The data source credentials were not applied during deployment.

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The Test workspace has a separate dataset that was manually created.

Question 3

You are modeling a many-to-many relationship between 'Student' and 'Class' tables. Which approach should you use in Power BI to handle this?

Accepted Answer

Add a bridge table with composite keys. A many-to-many relationship in Power BI requires a bridge (or junction) table that contains composite keys (e.g., StudentID and ClassID) to resolve the relationship into two one-to-many relationships. This allows Power BI to properly filter and aggregate data across both tables without ambiguity.

Answer

Merge both tables into one

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Use bidirectional cross-filtering

Answer

Create a single one-to-many relationship

Question 4

A Power BI report contains a page with many visuals that use a large DirectQuery dataset. The report is slow to load. Which design change would most improve the initial page load time?

Accepted Answer

Reduce the number of visuals on the page. Reducing the number of visuals on the page directly decreases the number of queries sent to the DirectQuery source during initial page load. Each visual in a DirectQuery model typically generates at least one separate query against the source database, so fewer visuals means fewer concurrent queries and less data transferred, which significantly improves load time.

Answer

Increase the default page-level filter to limit data

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Use a slicer to let users choose what to see

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Create aggregations on the dataset

Question 5

You have a Power BI report that uses a dataset with many columns. You want to reduce the dataset size by removing columns that are not used in any report visual. What is the best practice?

Accepted Answer

Remove the columns in Power Query Editor before loading. Removing columns in Power Query Editor before they are loaded into the data model physically excludes them from the dataset, reducing its size and improving performance. This is the only method that prevents unused columns from consuming memory and storage in the in-memory VertiPaq engine.

Answer

Use the Q&A feature to exclude columns

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Apply report-level filters to exclude the columns

Answer

Hide the columns in the model view

Question 6

You are connecting to an Excel workbook stored in Microsoft SharePoint Online. You want to refresh the data in Power BI service without manual intervention. Which type of gateway is required?

Accepted Answer

No gateway is required. When connecting to an Excel workbook stored in Microsoft SharePoint Online, the data source resides entirely in the cloud. Power BI service can directly access SharePoint Online via its cloud-to-cloud connectivity using the same Microsoft Entra ID authentication context. Therefore, no on-premises data gateway is required for scheduled refresh because the data never traverses an on-premises network.

Answer

On-premises data gateway (standard mode)

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On-premises data gateway (personal mode)

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Virtual network (VNet) gateway

Question 7

You are importing data from an Excel workbook that has multiple worksheets. You only need data from the 'Sales' worksheet. When you connect via Power Query, all worksheets appear in the Navigator. What should you do to load only the 'Sales' worksheet?

Accepted Answer

Select the 'Sales' worksheet in Navigator and click 'Load'. In Power Query, the Navigator pane allows you to select specific worksheets or tables to load. Selecting the 'Sales' worksheet and clicking 'Load' imports only that data into your data model, avoiding unnecessary data. This is the most efficient method because it directly targets the required worksheet without extra steps.

Answer

Load all worksheets, then delete the unwanted ones

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Select all worksheets and click 'Load'

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Select the 'Sales' worksheet and click 'Transform Data'

Question 8

During data refresh in Power BI, an error occurs: 'The column 'OrderID' of the table 'Orders' contains a duplicate value and this column is part of a primary key.' The table 'Orders' is imported from an Azure SQL database. What is the most likely cause of this error?

Accepted Answer

The source table has duplicate 'OrderID' values.. The error message explicitly states that the 'OrderID' column contains a duplicate value and is part of a primary key. In Power BI, when importing from a source like Azure SQL Database, the data model enforces uniqueness on primary key columns. If the source table has duplicate 'OrderID' values, the refresh fails because Power BI cannot maintain the required unique constraint.

Answer

The 'Orders' table was reordered in Power Query.

Answer

Data type mismatch between the source and Power BI.

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A calculated column is referencing the 'Orders' table.

Question 9

You are importing a large dataset from a CSV file using Power Query. The file contains 50 columns, but you only need 10 for your report. What is the most efficient way to reduce the amount of data loaded into the model?

Accepted Answer

Remove the unnecessary columns in Power Query before loading.. Power Query processes data before it enters the Power BI model. Removing unnecessary columns at the query stage reduces the amount of data loaded into memory, improving performance and reducing storage. This is the most efficient approach as it minimizes the dataset size from the start, unlike post-load methods that still consume resources.

Answer

Load all columns and then hide the unnecessary ones in the report.

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Use a SQL query to select only the needed columns if the data source supports it.

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Create a DAX calculated table that selects only the needed columns.

Question 10

A company uses Power BI to analyze sales data from a SQL Server database. The database contains a table 'Sales' with 10 million rows. The business analysts need to create daily reports that aggregate sales by region and product category. To optimize report performance, which data preparation technique should be applied?

Accepted Answer

Perform aggregation in SQL before importing.. Performing aggregation in SQL before importing reduces the data volume from 10 million rows to a much smaller aggregated result set. This minimizes memory consumption and speeds up report rendering in Power BI, as the heavy lifting is done on the SQL Server engine rather than in Power Query or the Power BI data model.

Answer

Increase the row limit in Power Query to load all rows.

Answer

Remove unused columns from the query.

Answer

Import the entire table and aggregate in Power BI.