The correct answer is that CALCULATE returns blank because there are no sales in the previous year period. When SAMEPERIODLASTYEAR is used inside CALCULATE, it shifts the current filter context to the prior year; if that prior period contains no sales rows, the filter context returns an empty table, causing CALCULATE to output BLANK. This blank then flows into the DIVIDE function, which returns blank for the 'Sales YoY %' measure even though the denominator is not zero. On the PL-300 exam, this scenario tests your understanding of how time intelligence functions interact with filter context and empty tables—a common trap is assuming DIVIDE handles missing numerators gracefully, but it only avoids division-by-zero errors, not blank numerators. To remember: SAMEPERIODLASTYEAR does not create sales; it only shifts dates, so no prior sales means no prior rows, and CALCULATE returns blank, not zero.
PL-300 Prepare the data Practice Question
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.
Exhibit
Refer to the exhibit.
// DAX Measure in a Power BI dataset
Total Sales =
SUMX(
Sales,
Sales[Quantity] * Sales[UnitPrice]
)
// Another measure
Sales LY =
CALCULATE(
[Total Sales],
SAMEPERIODLASTYEAR('Date'[Date])
)
// Then a third measure
Sales YoY % =
DIVIDE(
[Total Sales] - [Sales LY],
[Sales LY]
)
Refer to the exhibit. You have a Power BI dataset with the measures shown. When you use 'Sales YoY %' in a visual, it returns blank for months that have no sales in the previous year. 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.
Refer to the exhibit.
// DAX Measure in a Power BI dataset
Total Sales =
SUMX(
Sales,
Sales[Quantity] * Sales[UnitPrice]
)
// Another measure
Sales LY =
CALCULATE(
[Total Sales],
SAMEPERIODLASTYEAR('Date'[Date])
)
// Then a third measure
Sales YoY % =
DIVIDE(
[Total Sales] - [Sales LY],
[Sales LY]
)
A
CALCULATE returns blank because there are no sales in the previous year period.
If no sales exist in the previous year, the measure returns blank, causing DIVIDE to return blank.
B
The Date table does not contain dates for the previous year.
Why wrong: The Date table typically includes all dates.
C
The SAMEPERIODLASTYEAR function is not supported in this context.
Why wrong: It is supported.
D
DIVIDE function returns blank when denominator is zero.
Why wrong: DIVIDE returns blank when denominator is zero, but here the denominator is blank, not zero.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
CALCULATE returns blank because there are no sales in the previous year period.
Option A is correct because when using SAMEPERIODLASTYEAR inside CALCULATE, if there are no sales in the previous year for a given month, the filter context returns an empty table, causing CALCULATE to return BLANK. This blank propagates to the DIVIDE function, which then returns blank for the 'Sales YoY %' measure, even though the denominator is not zero.
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.
✓
CALCULATE returns blank because there are no sales in the previous year period.
Why this is correct
If no sales exist in the previous year, the measure returns blank, causing DIVIDE to return 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.
✗
The Date table does not contain dates for the previous year.
Why it's wrong here
The Date table typically includes all dates.
✗
The SAMEPERIODLASTYEAR function is not supported in this context.
Why it's wrong here
It is supported.
✗
DIVIDE function returns blank when denominator is zero.
Why it's wrong here
DIVIDE returns blank when denominator is zero, but here the denominator is blank, not zero.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates mistakenly attribute the blank to DIVIDE's zero-denominator behavior, when in fact the blank originates from CALCULATE returning no data due to missing prior-year sales.
Detailed technical explanation
How to think about this question
Under the hood, SAMEPERIODLASTYEAR shifts the current filter context by exactly one year, returning a set of dates. If no sales exist for those dates, the measure evaluates to BLANK. DIVIDE handles BLANK denominators gracefully by returning BLANK, but the root cause is the empty filter context from CALCULATE. In real-world scenarios, this often occurs with new products or seasonal data where prior-year periods have no transactions.
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.
TExam Day Tips
→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 exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Prepare the data — This question tests Prepare the data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: CALCULATE returns blank because there are no sales in the previous year period. — Option A is correct because when using SAMEPERIODLASTYEAR inside CALCULATE, if there are no sales in the previous year for a given month, the filter context returns an empty table, causing CALCULATE to return BLANK. This blank propagates to the DIVIDE function, which then returns blank for the 'Sales YoY %' measure, even though the denominator is not zero.
What should I do if I get this PL-300 question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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.
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