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 are merging two queries in Power Query: 'Orders' and 'Customers'. The 'Orders' table has a 'CustomerID' column, and 'Customers' has 'CustomerID' and 'Name'. You need to bring the 'Name' into 'Orders' but only for matching CustomerIDs; unmatched rows should be removed. Which join kind should you use?
Right Anti
Why wrong: Keeps rows from Customers that have no match in Orders.
Full Outer
Why wrong: Keeps all rows from both tables.
Inner
Only matching rows from both tables are kept.
Left Outer
Why wrong: Retains all Orders rows, including unmatched.
Answer choices
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
Inner
The Inner join kind in Power Query returns only rows where there is a match in both tables based on the key columns. Since the requirement is to bring the 'Name' into 'Orders' only for matching CustomerIDs and to remove unmatched rows, the Inner join is the correct choice. It ensures that only orders with a corresponding customer in the 'Customers' table are retained, and the 'Name' column is added to those matching rows.
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.
Right Anti
Why it's wrong here
Keeps rows from Customers that have no match in Orders.
Full Outer
Why it's wrong here
Keeps all rows from both tables.
Inner
Why this is correct
Only matching rows from both tables are kept.
Related concept
Read the scenario before looking for a memorised answer.
Left Outer
Why it's wrong here
Retains all Orders rows, including unmatched.
Common exam traps
The trap here is that candidates often confuse Left Outer join with Inner join, thinking that 'bringing in data only for matches' means keeping all left rows, but Left Outer retains unmatched left rows with nulls, while Inner removes them entirely.
Detailed technical explanation
Under the hood, Power Query's merge operation uses a hash-based lookup to match rows on the key columns; an Inner join filters the left table to only rows that have at least one match in the right table, then expands the matching columns. A subtle behavior is that if there are duplicate CustomerIDs in the 'Customers' table, an Inner join will multiply the rows in 'Orders' (one per match), which can cause unexpected row inflation if not handled with deduplication. In a real-world scenario, this is critical when merging sales orders with a customer dimension table that should have unique keys to avoid data duplication.
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: Inner — The Inner join kind in Power Query returns only rows where there is a match in both tables based on the key columns. Since the requirement is to bring the 'Name' into 'Orders' only for matching CustomerIDs and to remove unmatched rows, the Inner join is the correct choice. It ensures that only orders with a corresponding customer in the 'Customers' table are retained, and the 'Name' column is added to those matching rows.
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.
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Last reviewed: Jun 24, 2026
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