Quick Answer
The answer is DISTINCTCOUNT(Students[StudentID]). This measure correctly counts unique students in a many-to-many relationship because the filter from Courses propagates through the Enrollments junction table to the Students table, and DISTINCTCOUNT ensures each student is counted only once regardless of how many courses they take. On the Microsoft Power BI Data Analyst PL-300 exam, this scenario tests your understanding of how DAX handles many-to-many relationships via bidirectional filtering or cross-filter direction; a common trap is choosing COUNTROWS(Enrollments), which counts enrollments rather than students, or using COUNT(Students[StudentID]), which might include duplicates. The key insight is that DISTINCTCOUNT inherently respects the relationship chain, making it the safest and most accurate choice for counting students enrolled in at least one course. Memory tip: think “DISTINCTCOUNT for distinct people” — when you need a headcount across a bridge table, always reach for DISTINCTCOUNT on the student ID column.
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.
You are modeling a many-to-many relationship between 'Students' and 'Courses' via a junction table 'Enrollments'. You need to create a measure that counts the number of students enrolled in at least one course. The relationship between Students and Enrollments is one-to-many, and between Courses and Enrollments is one-to-many. What DAX measure should you use?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "least"
Why it matters: You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
COUNTROWS(Enrollments)
Why wrong: Counts enrollments, not students.
COUNT(Courses[CourseID])
Why wrong: Counts courses.
COUNTA(Students[StudentID])
Why wrong: COUNTA counts non-blank values but may not handle filter context as well.
DISTINCTCOUNT(Students[StudentID])
Counts unique students, works with many-to-many.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
DISTINCTCOUNT(Students[StudentID])
Option B is correct. DISTINCTCOUNT on Students[StudentID] counts unique students, which works correctly with many-to-many because the filter from Courses propagates to Enrollments and then to Students. Option A counts rows in Enrollments, which could be multiple per student. Option C counts courses, not students. Option D counts students but only those with enrollments; however, the filter context may cause blanks. DISTINCTCOUNT is safer.
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.
COUNTROWS(Enrollments)
Why it's wrong here
Counts enrollments, not students.
COUNT(Courses[CourseID])
Why it's wrong here
Counts courses.
COUNTA(Students[StudentID])
Why it's wrong here
COUNTA counts non-blank values but may not handle filter context as well.
DISTINCTCOUNT(Students[StudentID])
Why this is correct
Counts unique students, works with many-to-many.
Clue confirmation
The clue word "least" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
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: DISTINCTCOUNT(Students[StudentID]) — Option B is correct. DISTINCTCOUNT on Students[StudentID] counts unique students, which works correctly with many-to-many because the filter from Courses propagates to Enrollments and then to Students. Option A counts rows in Enrollments, which could be multiple per student. Option C counts courses, not students. Option D counts students but only those with enrollments; however, the filter context may cause blanks. DISTINCTCOUNT is safer.
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.
Yes — watch for: "least". You want the option with minimum overhead, fewest steps, or lowest impact — not the most feature-rich or comprehensive answer.
Read the scenario before looking for a memorised answer.
About these practice questions
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Same concept, more angles
These questions test the same concept from different angles. Work through them to make sure you can recognise it however the exam phrases it.
Variation 1. You need to create a relationship between two tables where one table has duplicate values on the key column. Which cardinality should you choose?
easyWhy C: Option B is correct: Many-to-one is used when the lookup table has unique values and the fact table has duplicates. Option A is wrong because one-to-many is the reverse. Option C is wrong because many-to-many is for when both sides have duplicates. Option D is wrong because one-to-one is for unique keys on both sides.
Variation 2. When creating a many-to-many relationship between two tables, what is a common approach to model this in Power BI?
easyWhy C: Option B is correct because a bridge table resolves many-to-many relationships by creating two one-to-many relationships. Option A is wrong because a single many-to-many relationship without a bridge table is not supported directly. Option C is wrong because CROSSJOIN creates a Cartesian product, which is not correct. Option D is wrong because merging tables into one removes the relationship structure.
Variation 3. You are modeling data with a many-to-many relationship between 'Student' and 'Class' tables. Which THREE configurations can handle this scenario?
hardWhy A: Options A, B, and C are correct. Option A uses a bridge table which is the standard approach. Option B uses a calculated column concatenation for limited scenarios. Option C uses CROSSFILTER to enable many-to-many filtering. Option D is wrong because removing duplicates loses information. Option E is wrong because changing to one-to-many incorrectly assumes uniqueness.
Last reviewed: Jun 21, 2026
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