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

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

Answer: (A)

The main idea here is how the RIGHT JOIN works: it returns all rows from the right table and the matching rows from the left, filling in NULLs for the left-side columns when there is no match. This is useful when you want to keep every record from the right table regardless of whether there’s a corresponding row in the left table.

For example, if the right table lists customers and the left table lists orders linked by customer ID, a RIGHT JOIN on that key would include every customer from the right table. If a customer has an order, the order data appears from the left; if not, the left-side fields show NULL.

This behavior differs from the other join types: a LEFT JOIN would keep all rows from the left table instead, an INNER JOIN would only include rows where there’s a match in both tables, and a FULL OUTER JOIN would bring in all rows from both tables, with NULLs where there’s no match.