This PL-300 practice question tests your understanding of model 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.
Which TWO of the following are best practices for designing a star schema in Power BI?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue: "best"
Why it matters: Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
Dimension tables should have a primary key and descriptive columns.
Option A is correct because dimension tables in a star schema are designed to store descriptive attributes (e.g., product name, category) and must have a primary key column that uniquely identifies each row. This primary key is referenced by foreign keys in fact tables, enabling efficient filtering and slicing in Power BI. Without a primary key, relationships cannot be properly enforced, leading to ambiguous or incorrect query results.
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.
✓
Dimension tables should have a primary key and descriptive columns.
Why this is correct
This is a basic star schema design principle.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Fact tables should contain calculated columns for business logic.
Why it's wrong here
Calculated columns are not recommended in fact tables; measures are preferred.
✓
Fact tables should have foreign keys that relate to dimension tables.
Why this is correct
Foreign keys ensure relationships between fact and dimension tables.
Clue confirmation
The clue word "best" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
✗
Merge all tables into a single flat table for simplicity.
Why it's wrong here
This is the opposite of star schema.
✗
Use many-to-many relationships between fact and dimension tables.
Why it's wrong here
Star schema uses one-to-many relationships.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse calculated columns with measures, thinking that placing business logic in fact tables is acceptable, but Power BI best practices dictate that measures (calculated at query time) should be used instead to avoid inflating the model size and degrading performance.
Detailed technical explanation
How to think about this question
In a star schema, dimension tables are denormalized to contain all descriptive attributes for a business entity (e.g., customer, product, date), and each dimension table has a surrogate key (often an integer identity column) that serves as the primary key. Fact tables store quantitative measures (e.g., sales amount, quantity) and foreign keys that reference these dimension primary keys, enabling efficient star-join operations. Power BI's VertiPaq engine compresses data column-by-column, so storing descriptive columns in dimensions rather than in the fact table significantly reduces memory usage and improves query performance, especially for large datasets.
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.
Model the data — This question tests Model the data — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: Dimension tables should have a primary key and descriptive columns. — Option A is correct because dimension tables in a star schema are designed to store descriptive attributes (e.g., product name, category) and must have a primary key column that uniquely identifies each row. This primary key is referenced by foreign keys in fact tables, enabling efficient filtering and slicing in Power BI. Without a primary key, relationships cannot be properly enforced, leading to ambiguous or incorrect query results.
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: "best". Signals that multiple options may be partially correct. Choose the option that most directly solves the exact problem described, not the one that sounds most complete.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
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Question Discussion
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