DA0-002 Data Concepts and Environments Practice Question
A data analyst needs to combine rows from two tables based on a related column, but only wants rows that have matching values in both tables. Which join type should the analyst use?
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
✓
INNER JOIN
INNER JOIN returns only rows with matching values in both tables, which matches the requirement.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
RIGHT JOIN
Why it's wrong here
RIGHT JOIN returns all rows from the right table.
- ✓
INNER JOIN
Why this is correct
INNER JOIN returns only matching rows.
- ✗
FULL OUTER JOIN
Why it's wrong here
A FULL OUTER JOIN returns all rows from both tables, including non-matching rows with NULLs where no match exists, which violates the requirement to retain only rows with matching values. It is tempting because it does combine rows based on a related column, and would be correct if the analyst needed to preserve unmatched rows from both sides for a complete dataset audit.
- ✗
LEFT JOIN
Why it's wrong here
LEFT JOIN returns all rows from the left table.
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