Quick Answer
The answer is SAMEPERIODLASTYEAR. This DAX function is the most direct and precise choice for calculating previous year sales in Power BI because it automatically shifts the entire current date context back by one year, returning a contiguous set of dates from the prior year. While DATEADD can achieve the same result with a -1 year interval, SAMEPERIODLASTYEAR is specifically designed for year-over-year comparisons and is the preferred function on the Microsoft Power BI Data Analyst PL-300 exam when the requirement explicitly states “previous year.” This question tests your understanding of time intelligence functions and their specific use cases, a common topic in the exam’s “Modeling” section. A frequent trap is confusing PREVIOUSYEAR with SAMEPERIODLASTYEAR—remember that PREVIOUSYEAR is not a valid DAX function, so it will never be the correct answer. For a quick memory tip: think of “same period, last year” as the literal name of the function, which directly matches the search intent for previous year sales DAX function.
This PL-300 practice question tests your understanding of model 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.
A data model contains a Date table and a Sales table. You need to create a measure that calculates total sales for the previous year. Which DAX function should you use?
SAMEPERIODLASTYEAR
SAMEPERIODLASTYEAR returns a set of dates in the previous year corresponding to the current selection.
DATEADD
Why wrong: DATEADD can shift dates by any interval, but for previous year SAMEPERIODLASTYEAR is more specific.
PARALLELPERIOD
Why wrong: PARALLELPERIOD returns a period shifted by a given number of intervals, but not specifically previous year.
PREVIOUSYEAR
Why wrong: PREVIOUSYEAR is not a valid DAX function.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
SAMEPERIODLASTYEAR
Option B is correct because SAMEPERIODLASTYEAR returns a set of dates shifted back one year. Option A (DATEADD) can also be used but is more general. Option C (PREVIOUSYEAR) is not a valid DAX function. Option D (PARALLELPERIOD) returns a parallel period but not necessarily the previous year.
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.
SAMEPERIODLASTYEAR
Why this is correct
SAMEPERIODLASTYEAR returns a set of dates in the previous year corresponding to the current selection.
Related concept
Read the scenario before looking for a memorised answer.
DATEADD
Why it's wrong here
DATEADD can shift dates by any interval, but for previous year SAMEPERIODLASTYEAR is more specific.
PARALLELPERIOD
Why it's wrong here
PARALLELPERIOD returns a period shifted by a given number of intervals, but not specifically previous year.
PREVIOUSYEAR
Why it's wrong here
PREVIOUSYEAR is not a valid DAX function.
Common exam traps
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
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.
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
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.
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FAQ
Model the data — This question tests Model the data — Read the scenario before looking for a memorised answer..
The correct answer is: SAMEPERIODLASTYEAR — Option B is correct because SAMEPERIODLASTYEAR returns a set of dates shifted back one year. Option A (DATEADD) can also be used but is more general. Option C (PREVIOUSYEAR) is not a valid DAX function. Option D (PARALLELPERIOD) returns a parallel period but not necessarily the previous year.
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.
Read the scenario before looking for a memorised answer.
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Last reviewed: Jun 21, 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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