Which join type returns all rows from the left table, even if there are no matches in the right table?

Which join type returns all rows from the left table, even if there are no matches in the right table?

• A. Cross Joins
• B. Inner Join
• C. Full joins
• D. Left (or Right) Join

Answer: (D)

This question tests understanding of how outer joins preserve rows from one side. A left outer join keeps every row from the left table and, when there isn’t a matching row in the right table, fills the right-side columns with NULLs. That means you’ll always see all the left-side rows in the result, even if there’s no corresponding row on the right. Cross joins produce every possible pair of rows from both tables, not tied to matches. Inner joins return only rows where there is a match on both sides. Full outer joins return all rows from both tables, including unmatched right-side rows, which means the result isn’t focused solely on preserving the left table’s rows.

This question tests understanding of how outer joins preserve rows from one side. A left outer join keeps every row from the left table and, when there isn’t a matching row in the right table, fills the right-side columns with NULLs. That means you’ll always see all the left-side rows in the result, even if there’s no corresponding row on the right.

Cross joins produce every possible pair of rows from both tables, not tied to matches. Inner joins return only rows where there is a match on both sides. Full outer joins return all rows from both tables, including unmatched right-side rows, which means the result isn’t focused solely on preserving the left table’s rows.