Quick Answer
The answer is to use Replace Values in the Power Query Editor to replace null with 0. This is the most efficient transformation because Replace Values operates directly on the column at the query level, allowing Power Query to handle nulls before the data ever reaches the data model, avoiding costly post-load cleanup. On the Microsoft Power BI Data Analyst PL-300 exam, this scenario tests your understanding of Power Query’s M language and its built-in data cleaning tools, often appearing in questions about handling incomplete SQL Server imports. A common trap is to attempt a conditional column or an IF statement in DAX, but those are less efficient and run after loading. The key insight is that Power Query’s Replace Values is purpose-built for this exact task, making it the fastest and most direct method. Memory tip: think “Replace Values, not replace formulas”—if you see null, just swap it for zero in the query editor.
This PL-300 practice question tests your understanding of prepare the data. Read the scenario carefully and evaluate each option against the stated constraints before committing to an answer. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
You are loading data from a SQL Server database into Power BI. The source table contains a column 'SalesAmount' with occasional NULL values. In the Power Query Editor, you need to replace NULLs with 0 before loading. What is the most efficient transformation?
Use 'Replace Errors' with value 0.
Why wrong: Replace Errors only handles errors, not nulls.
Use 'Fill Down' to fill nulls with the previous value.
Why wrong: Fill Down does not guarantee 0.
Use 'Replace Values' to replace null with 0.
Directly replaces nulls with 0 in one step.
Use 'Change Type' to convert to a non-nullable type.
Why wrong: Changing type does not replace null values.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Use 'Replace Values' to replace null with 0.
Option C is correct because 'Replace Values' in Power Query Editor is specifically designed to replace null values with a specified value, such as 0. This transformation is the most efficient and direct method for handling NULLs in a column, as it operates at the query level before data is loaded into the Power BI data model.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
For each option: why learners choose it and why it is or isn't the right answer here.
Use 'Replace Errors' with value 0.
Why it's wrong here
Replace Errors only handles errors, not nulls.
Use 'Fill Down' to fill nulls with the previous value.
Why it's wrong here
Fill Down does not guarantee 0.
Use 'Replace Values' to replace null with 0.
Why this is correct
Directly replaces nulls with 0 in one step.
Related concept
Read the scenario before looking for a memorised answer.
Use 'Change Type' to convert to a non-nullable type.
Why it's wrong here
Changing type does not replace null values.
Common exam traps
The trap here is that candidates may confuse 'Replace Errors' with 'Replace Values', mistakenly thinking NULLs are errors, or they may overcomplicate the solution by using 'Fill Down' or type changes instead of the direct replacement method.
Detailed technical explanation
Under the hood, Power Query's 'Replace Values' uses the M function Table.ReplaceValue, which efficiently scans the column and substitutes null with the specified replacement. This operation is performed in-memory during query folding where possible, minimizing data movement. In real-world scenarios, replacing NULLs with 0 in SalesAmount ensures accurate aggregations (e.g., SUM, AVERAGE) without skewing results, as NULLs would otherwise be ignored in calculations.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
A cloud solutions architect for a retail company is evaluating services for a new workload. The correct answer here reflects best practice for the specific scenario described — not a general cloud recommendation. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Cloud exam questions reward reading the constraint carefully: the same technology can be right or wrong depending on the use case.
What to study next
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FAQ
Prepare the data — This question tests Prepare the data — Read the scenario before looking for a memorised answer..
The correct answer is: Use 'Replace Values' to replace null with 0. — Option C is correct because 'Replace Values' in Power Query Editor is specifically designed to replace null values with a specified value, such as 0. This transformation is the most efficient and direct method for handling NULLs in a column, as it operates at the query level before data is loaded into the Power BI data model.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 24, 2026
This PL-300 practice question is part of Courseiva's free Microsoft certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PL-300 exam.
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