PL-300 Prepare the data Practice Question
You are importing data from an Excel workbook that contains a column 'Region' with values such as 'North', 'South', 'East', 'West', and some blank cells. You need to replace the blank cells with 'Unknown' to ensure consistent reporting. What is the most efficient way to achieve this in Power Query?
⚠ Common exam trap
The trap here is overcomplicating the solution by considering conditional columns or filtering, when a simple replace operation suffices.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Use the 'Replace Values' feature to replace null with 'Unknown'.
Using 'Replace Values' to replace null with 'Unknown' directly modifies the column in place, ensuring all blanks become 'Unknown' without adding extra columns or removing rows. This is the most efficient and straightforward method for this data cleansing task.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✓
Use the 'Replace Values' feature to replace null with 'Unknown'.
Why this is correct
The 'Replace Values' feature in Power Query can replace null values with a specified text. This is a straightforward and efficient method to handle blanks in a single column. It does not require complex coding and is a common data cleansing step.
- ✗
Filter out the rows where 'Region' is blank.
Why it's wrong here
Filtering out blank rows would remove data, which is not desired because the requirement is to replace blanks with 'Unknown', not to exclude them. This would lead to incomplete reporting and potentially skew results. It does not meet the requirement of consistent reporting with 'Unknown' for blanks.
- ✗
Add a conditional column that checks if 'Region' is null and returns 'Unknown'.
Why it's wrong here
While a conditional column can achieve the result, it creates a new column rather than modifying the existing one. This adds an extra step and may require removing the original column. The 'Replace Values' feature is more direct and efficient for this simple replacement task.
- ✗
Use the 'Fill Down' feature to fill blanks with the value from the row above.
Why it's wrong here
Fill Down is used to fill blanks with the value from the previous row, which is not appropriate here because the blanks do not necessarily belong to the same region as the row above. This could introduce incorrect data. The requirement is to replace blanks with a specific value, not to propagate values.
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Last reviewed September 2026 · checked against the official Microsoft exam blueprint
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