Which join type returns all rows from both tables, including unmatched rows?

Which join type returns all rows from both tables, including unmatched rows?

• A. INNER JOIN
• B. FULL OUTER JOIN
• C. LEFT JOIN
• D. RIGHT JOIN

Answer: (B)

Understanding how different SQL joins decide which rows to include is what this question is about. An inner join returns only the rows where there is a match in both tables, so unmatched rows from either side are not included. A left join keeps every row from the left table and brings in matching rows from the right; if there’s no match on the right, you get NULLs for the right-side columns. A right join does the opposite, preserving all rows from the right table with NULLs on the left when there’s no match. A full outer join, on the other hand, includes every row from both tables. If a row has a matching counterpart in the other table, you see the combined data; if not, the missing side is filled with NULLs. This means you capture all data from both datasets, unmatched or not. That is why the full outer join is the best choice for returning all rows from both tables, including unmatched ones.

Understanding how different SQL joins decide which rows to include is what this question is about. An inner join returns only the rows where there is a match in both tables, so unmatched rows from either side are not included. A left join keeps every row from the left table and brings in matching rows from the right; if there’s no match on the right, you get NULLs for the right-side columns. A right join does the opposite, preserving all rows from the right table with NULLs on the left when there’s no match.

A full outer join, on the other hand, includes every row from both tables. If a row has a matching counterpart in the other table, you see the combined data; if not, the missing side is filled with NULLs. This means you capture all data from both datasets, unmatched or not. That is why the full outer join is the best choice for returning all rows from both tables, including unmatched ones.