PL-300 Prepare the data Practice Test 8 — 15 Questions

Question 1

Refer to the exhibit. You are configuring a data source in Power BI Service using a JSON policy. The data source fails to refresh. What is the most likely issue?

Accepted Answer

The service principal does not have permission to the Azure SQL Database.. When using a JSON policy with a service principal in Power BI, the service principal must have the necessary permissions (e.g., db_datareader role) on the Azure SQL Database. Without these permissions, the data source will fail to refresh, as Power BI cannot authenticate or access the data. The JSON policy itself may be syntactically valid, but the underlying authentication fails due to insufficient database-level permissions.

Answer

The version value should be "2.0".

Answer

The JSON is missing the 'dataSource' type.

Answer

The connection string is missing the database name.

Question 2

You are importing a large CSV file (200 MB) into Power BI Desktop. The import is very slow and sometimes fails. What should you do to improve performance?

Accepted Answer

Filter rows and columns during import using Power Query to reduce data size.. Filtering rows and columns via Power Query is the correct approach to reduce the data loaded into the Power BI Desktop model. However, query folding does not apply to CSV files — it is a technique for database sources. For CSV, Power Query reads the entire file but still reduces memory and processing overhead by discarding unnecessary columns and rows before loading into the model. This is a standard best practice for large flat files.

Answer

Use Power BI Service to import the file instead.

Answer

Remove all relationships before import.

Answer

Upgrade to Power BI Premium.

Question 3

You need to combine two tables: Sales and Products, where Sales has a ProductID column and Products has a ProductKey column. The tables have a many-to-one relationship. Which Power Query transformation should you use?

Accepted Answer

Merge Queries.. Merge Queries (C) is correct because it performs a join between two tables based on matching columns, which is exactly what is needed to combine Sales and Products using ProductID and ProductKey. This transformation supports many-to-one relationships and allows you to expand related columns from the Products table into the Sales table, enabling further data analysis.

Answer

Group By.

Answer

Append Queries.

Answer

Pivot Column.

Question 4

You have a table with a column 'Date' in text format (e.g., '2024-01-15'). You need to convert it to a date type. In Power Query, what is the best approach?

Accepted Answer

Change the column data type to Date in Power Query Editor.. In Power Query Editor, you can simply change the data type of the column from Text to Date. Power Query automatically parses common date formats like '2024-01-15'. Option A is incorrect because splitting the column into year, month, day and then combining is unnecessarily complex and error-prone; Power Query can directly convert. Option B is incorrect because the Excel Power Query add-in is not needed; Power Query is built into Power BI Desktop. Option C is incorrect because using a DAX calculated column with DATEVALUE is not the best approach in Power Query; DAX operates on the data model after data is loaded, whereas Power Query transformations should be done before loading. Changing the data type in Power Query is the most efficient and standard method.

Answer

Split the column into year, month, day and then combine.

Answer

Use the Excel Power Query add-in.

Answer

Create a calculated column in DAX using DATEVALUE.

Question 5

You are reviewing the M query snippet above. The query imports an Excel file and filters rows where Date is on or after January 1, 2024. However, the query fails with an error. What is the most likely cause?

Accepted Answer

The file path is local and may not be accessible after deployment.. The file path is hardcoded to a local drive, which may not exist after deployment to the Power BI Service or on another machine, causing a failure. Option A is incorrect because the data type conversion can handle null values if handled properly. Option B is incorrect because Excel.Workbook can read .xlsx files. Option C is incorrect because the date filter syntax appears correct.

Answer

The data type conversion cannot handle null values.

Answer

The Excel.Workbook function cannot read .xlsx files.

Answer

The date filter syntax is incorrect.

Question 6

You have a column 'ProductID' that contains integers. You need to ensure that this column is used as a key in relationships. What data type should the column have?

Accepted Answer

Whole Number.. In Power BI, relationship keys must be of a data type that supports exact matching and efficient indexing. Whole Number (integer) is the optimal type for primary keys in relationships, as it ensures unique, non-decimal values that Power BI can use for fast lookups and joins without precision issues.

Answer

Decimal Number.

Answer

Text.

Answer

Binary.

Question 7

Which TWO actions should you take to reduce the size of a Power BI dataset? (Choose two.)

Accepted Answer

Filter out rows that are not needed.. Filtering out unnecessary rows at the source reduces the number of rows loaded into the Power BI dataset, directly decreasing the data volume and storage size. This is a fundamental data reduction technique that minimizes memory consumption and improves refresh performance.

Answer

Disable query folding to improve performance.

Answer

Add calculated columns to precompute values.

Answer

Use DirectQuery instead of Import.

Question 8

Which THREE factors should you consider when choosing between Import and DirectQuery storage modes? (Choose three.)

Accepted Answer

Report interactivity and performance needs.. Import mode pre-aggregates data into an in-memory columnstore, enabling sub-second DAX query responses, while DirectQuery mode sends queries to the source database in real time, which can introduce latency. The choice between them directly impacts report interactivity and performance, as Import mode is optimized for fast, interactive slicing and dicing, whereas DirectQuery may suffer from slower response times on complex measures or large result sets.

Answer

User license type (Pro vs Premium).

Answer

Report color scheme and branding.

Question 9

Which TWO are valid ways to combine data from multiple sources in Power Query? (Choose two.)

Accepted Answer

Append Queries.. The Append Queries operation in Power Query combines rows from two or more tables by stacking them vertically, which is a standard way to consolidate data from multiple sources when the columns are aligned. This is distinct from merging, which combines columns based on matching keys.

Answer

Pivot Column.

Answer

Create relationships in the data model.

Answer

Group By.

Question 10

You are reviewing the M query above. The query connects to an Azure SQL database and filters orders after June 1, 2024. The query runs successfully in Power Query Editor, but when you close and apply, the data load fails. What is the most likely cause?

Accepted Answer

The database server is not accessible or credentials are missing.. The query runs successfully in Power Query Editor but fails during 'Close & Apply' because the editor uses a cached data preview, while the actual load requires a live connection to the Azure SQL database. The most likely cause is that the database server is inaccessible or the credentials are missing or expired at load time, which is a common connectivity issue in Power BI.

Answer

The date filter syntax is invalid.

Answer

The query has a syntax error in the let expression.

Answer

The column 'OrderDetails' does not exist.

Question 11

You are reviewing the DAX expression above. The DateTable is supposed to have a continuous date range from 2020 to 2025. However, when you use the Year column in a slicer, the data shows only 2024 values. What is the most likely cause?

Accepted Answer

The DateTable is not related to the fact table.. The slicer showing only 2024 values indicates that the DateTable is not related to the fact table. Without an active relationship, the slicer on the Year column cannot filter the fact table, so it defaults to showing only the current year (2024) or the first year in the DateTable. A proper relationship (e.g., one-to-many from DateTable[Date] to FactTable[Date]) is required for cross-filtering to work.

Answer

The ADDCOLUMNS function is not supported.

Answer

The DAX syntax for CALENDAR is incorrect.

Answer

The DateTable has too many rows.

Question 12

You need to create a date table in Power BI using DAX. Which function should you use to generate a continuous list of dates?

Accepted Answer

CALENDAR.. The CALENDAR function in DAX generates a single-column table of dates that starts from a specified start date and ends at a specified end date, creating a continuous list of all dates in that range. This is the correct function to use when you need to create a date table for time intelligence calculations in Power BI.

Answer

CALCULATE.

Answer

TODAY.

Answer

DATEVALUE.

Question 13

You are designing a Power BI data model for sales analysis. The source data includes a table with columns: OrderID, CustomerID, ProductID, OrderDate, Quantity, and UnitPrice. You need to support time intelligence calculations (e.g., year-to-date sales) and avoid creating a separate date table. What should you do?

Accepted Answer

Use the CALENDAR function in a calculated table to create a date table and mark it as a date table.. Time intelligence functions require a contiguous, marked date table. The only reliable way is to create a separate date table, which contradicts the stem's constraint. Auto date/time (B) creates hidden tables that cannot be used by DAX time intelligence. Therefore, as written, the question has no correct answer.

Answer

Enable the auto date/time option in Power BI Desktop settings.

Answer

Use the OrderDate column directly in time intelligence measures.

Answer

Create a calculated column for fiscal year using the OrderDate column.

Question 14

You are preparing data for a Power BI report. The source data has a column 'OrderDate' with date values. You need to create a date hierarchy for drill-down (Year, Quarter, Month). Which TWO actions are required?

Accepted Answer

Create a separate date table with a continuous range of dates.. To create a date hierarchy for drill-down (Year, Quarter, Month), you need a dedicated date table with a continuous range of dates (Option A) and mark it as a date table in Power BI Desktop (Option D). This ensures that all date periods are represented and that Power BI can use the table for time intelligence. Option B (auto date/time) is not required because you are creating your own date table. Option C (sorting by MonthNumber) is helpful for display order but not required for the hierarchy. Option E (calculated columns for Year, Quarter, Month) is unnecessary because these can be created using DAX functions within the date table, but the initial two required actions are A and D.

Answer

Enable auto date/time in Power BI Desktop.

Answer

Sort the Month column by MonthNumber to ensure proper order.

Answer

Add calculated columns for Year, Quarter, and Month to the date table.

Question 15

You are connecting Power BI to an Azure SQL Database. You need to ensure that the connection uses the most secure authentication method available. Which THREE options should you consider? (Choose three.)

Accepted Answer

Use a service principal with Microsoft Entra ID.. Using a service principal with Microsoft Entra ID (formerly Azure AD) enables token-based authentication for Power BI to Azure SQL Database, which is more secure than shared secrets or passwords. Service principals are non-interactive identities that can be granted fine-grained permissions, eliminating the need to store credentials and reducing the risk of credential exposure.

Answer

Use Windows authentication.

Answer

Use SQL Server authentication with a strong password.