Which SQL join type returns all matches and non-matches?

Which SQL join type returns all matches and non-matches?

• A. INNER JOIN returns matches.
• B. LEFT JOIN includes non-matching rows from the left side.
• C. RIGHT JOIN includes non-matching rows from the right side.
• D. FULL OUTER JOIN returns all matches and non-matches.

Answer: (D)

A FULL OUTER JOIN returns all matches and non-matches. It pulls every row from both tables, pairing rows where there is a match and, where there isn’t a counterpart, filling the missing side with NULLs. This means you see every row from both sides, whether a relationship exists or not. Other joins behave differently: an INNER JOIN shows only rows where keys match in both tables; a LEFT JOIN returns all rows from the left table plus any matching rows from the right (with NULLs on the right when there’s no match); a RIGHT JOIN does the same from the right side.

A FULL OUTER JOIN returns all matches and non-matches. It pulls every row from both tables, pairing rows where there is a match and, where there isn’t a counterpart, filling the missing side with NULLs. This means you see every row from both sides, whether a relationship exists or not.

Other joins behave differently: an INNER JOIN shows only rows where keys match in both tables; a LEFT JOIN returns all rows from the left table plus any matching rows from the right (with NULLs on the right when there’s no match); a RIGHT JOIN does the same from the right side.