The answer is that a Calendar table lacking a continuous date range is the most likely cause of blank year-over-year growth values. This occurs because the SAMEPERIODLASTYEAR function in DAX requires a contiguous set of dates to map the prior period correctly; if your Calendar table has gaps—such as missing months or an incomplete year—the function returns blank for those rows instead of a calculated value. On the Microsoft Power BI Data Analyst PL-300 exam, this tests your understanding of time intelligence functions and the critical requirement for a complete, uninterrupted date table. A common trap is assuming the DIVIDE function or relationship issues are at fault, but the core concept is that SAMEPERIODLASTYEAR cannot compute a prior period when the current period’s date has no matching prior date in the Calendar. To remember this, think of SAMEPERIODLASTYEAR as a bridge that needs both ends to exist—if your Calendar has a hole, the bridge collapses into blank.
PL-300 Visualize and analyze the data Practice Question
This PL-300 practice question tests your understanding of visualize and analyze the data. The scenario asks you to isolate a root cause — eliminate options that address a different problem before choosing. 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.
Exhibit
Refer to the exhibit.
```dax
Sales YoY % =
VAR CurrentSales = SUM(Sales[Amount])
VAR PreviousSales = CALCULATE(SUM(Sales[Amount]), SAMEPERIODLASTYEAR(Calendar[Date]))
RETURN
DIVIDE(CurrentSales - PreviousSales, PreviousSales, 0)
```
Refer to the exhibit. You have a DAX measure that calculates year-over-year sales growth. When you add this measure to a table visual with Year and Month, some rows show blank values. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "most likely"
Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
The Calendar table does not have a continuous date range, causing SAMEPERIODLASTYEAR to return blank for some months
Option B is correct because SAMEPERIODLASTYEAR requires a contiguous date range; missing dates in the Calendar table cause blank returns. Option A is wrong because DIVIDE handles division by zero. Option C is wrong because the measure uses SUM, not a relationship issue. Option D is wrong because the measure works at month granularity.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
✗
The measure cannot be used at the month level because SAMEPERIODLASTYEAR only works at year level
Why it's wrong here
SAMEPERIODLASTYEAR works at any date granularity.
✗
The measure is trying to divide by zero for months with no sales in the previous year
Why it's wrong here
DIVIDE has a third argument to return 0, so not blank.
✗
The relationship between Sales and Calendar is inactive
Why it's wrong here
The measure uses CALCULATE but doesn't specify a relationship; if active, it works.
✓
The Calendar table does not have a continuous date range, causing SAMEPERIODLASTYEAR to return blank for some months
Why this is correct
SAMEPERIODLASTYEAR requires a contiguous set of dates; missing dates cause blank.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
Common exam trap: answer the scenario, not the keyword
Many certification questions include familiar terms but test a specific constraint. Read the exact wording before choosing an answer that is generally true but wrong for this case.
Detailed technical explanation
How to think about this question
This question should be treated as a scenario, not a definition check. Identify the problem, the constraint and the best action. Then compare each option against those facts.
KKey Concepts to Remember
Read the scenario before looking for a memorised answer.
Find the constraint that changes the correct option.
Eliminate answers that are true in general but not in this case.
Use explanations to understand the rule behind the answer.
TExam Day Tips
→Underline the problem statement mentally.
→Watch for words such as best, first, most likely and least administrative effort.
→Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
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
Got this wrong? Here's your next step.
Identify which PL-300 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Visualize and analyze the data — This question tests Visualize and analyze the data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The Calendar table does not have a continuous date range, causing SAMEPERIODLASTYEAR to return blank for some months — Option B is correct because SAMEPERIODLASTYEAR requires a contiguous date range; missing dates in the Calendar table cause blank returns. Option A is wrong because DIVIDE handles division by zero. Option C is wrong because the measure uses SUM, not a relationship issue. Option D is wrong because the measure works at month granularity.
What should I do if I get this PL-300 question wrong?
Identify which PL-300 exam domain this question belongs to, then review the specific concept being tested. Practise related questions in that domain and focus on understanding why each wrong answer is tempting — not just why the correct answer is right.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
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Variation 1. 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?
medium
A.PARALLELPERIOD
B.DATEADD
✓ C.SAMEPERIODLASTYEAR
D.PREVIOUSYEAR
Why C: 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.
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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.
Question Discussion
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