Which JOIN type returns all rows from the left table and matched rows from the right?

Which JOIN type returns all rows from the left table and matched rows from the right?

• A. INNER JOIN returns only matched rows from both tables.
• B. FULL OUTER JOIN returns all rows where there is a match.
• C. RIGHT JOIN returns all rows from the right table and matched from the left.
• D. LEFT JOIN returns all rows from the left table and matched rows from the right.

Answer: (D)

Left join preserves every row from the left table and brings in the matching data from the right table when it exists. If there isn’t a corresponding row in the right table, the right-side columns appear as NULLs. This is useful when you want to keep the full set of records from the left side while optionally enriching them with related information from the right.

This differs from an inner join, which only returns rows that have matches on both sides, effectively dropping any left-side rows without a right-side match. It also differs from a full outer join, which returns every row from both tables, filling in NULLs where there’s no match on the opposite side. A right join does the opposite of a left join, keeping all rows from the right table and filling in NULLs on the left when there’s no match.

So the behavior described—keeping all rows from the left and including matched data from the right—fits a left join.