Quick Answer
The answer is Left Outer Join. This join type is correct because it returns all rows from the first table, 'Orders', and only the matching rows from the second table, 'Returns', based on the 'OrderID' column, ensuring no order is dropped even if it has no corresponding return. In the context of the Microsoft Power BI Data Analyst PL-300 exam, this question tests your understanding of table merging in Power Query, specifically how to preserve the left table’s integrity while enriching it with related data from a right table. A common trap is confusing Left Outer with Inner Join, which would exclude orders without returns. To remember, think of the left outer join as “keep everything on the left, add matches from the right”—the left table is the boss, and the right table is optional.
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.
You need to combine two tables from different sources: 'Orders' from SQL Server and 'Returns' from an Excel file. Both tables have a column named 'OrderID'. You want to include all orders and only matching returns. Which join type should you use in Power Query?
Inner Join
Why wrong: Inner join only returns rows where there is a match in both tables.
Right Outer Join
Why wrong: Right outer join returns all rows from the second table (Returns) and matching from Orders.
Full Outer Join
Why wrong: Full outer join returns all rows from both tables.
Left Outer Join
Left outer join returns all rows from the first table and matching rows from the second.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Left Outer Join
In Power Query, a Left Outer Join returns all rows from the first (left) table ('Orders') and only the matching rows from the second (right) table ('Returns'), based on the 'OrderID' column. This matches the requirement to include all orders and only matching returns, ensuring no order is dropped even if it has no corresponding return.
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.
Inner Join
Why it's wrong here
Inner join only returns rows where there is a match in both tables.
Right Outer Join
Why it's wrong here
Right outer join returns all rows from the second table (Returns) and matching from Orders.
Full Outer Join
Why it's wrong here
Full outer join returns all rows from both tables.
Left Outer Join
Why this is correct
Left outer join returns all rows from the first table and matching rows from the second.
Related concept
Read the scenario before looking for a memorised answer.
Common exam traps
The trap here is that candidates often confuse Left Outer Join with Right Outer Join, mistakenly thinking they need to include all returns instead of all orders, or they default to Inner Join without considering the requirement to preserve unmatched rows from the left table.
Detailed technical explanation
In Power Query's M language, the Table.Join function with JoinKind.LeftOuter performs this operation by preserving the left table's row count and adding nulls for missing right-side columns. A real-world scenario is merging sales orders with returns data where you need to keep every order for reporting, even if no return exists, to avoid losing order-level metrics.
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
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FAQ
Prepare the data — This question tests Prepare the data — Read the scenario before looking for a memorised answer..
The correct answer is: Left Outer Join — In Power Query, a Left Outer Join returns all rows from the first (left) table ('Orders') and only the matching rows from the second (right) table ('Returns'), based on the 'OrderID' column. This matches the requirement to include all orders and only matching returns, ensuring no order is dropped even if it has no corresponding return.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
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 combine two tables: Sales and Products, where Sales has a ProductID column and Products has a ProductKey column. The tables have a many-to-one relationship. Which Power Query transformation should you use?
easyWhy C: Merge Queries (C) is correct because it performs a join between two tables based on matching columns, which is exactly what is needed to combine Sales and Products using ProductID and ProductKey. This transformation supports many-to-one relationships and allows you to expand related columns from the Products table into the Sales table, enabling further data analysis.
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Last reviewed: Jun 24, 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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