Which statement correctly describes an outer join?

• A. Outer join returns only matching rows.
• B. Outer join includes all rows from one table and only matches from the other.
• C. Outer join returns a Cartesian product.
• D. Outer join sorts results by join key.

Answer: (B)

Outer joins keep every row from one side of the join and bring in the matching rows from the other side, filling in NULLs when there’s no match. This is exactly what the statement describes: you include all rows from one table and only the rows that have a counterpart in the other table. For example, a left outer join of customers to orders returns every customer, and if a customer has no orders, the order fields appear as NULL. This differs from an inner join, which would drop customers without orders; a Cartesian product would occur if there were no join condition at all, producing every combination of rows; and sorting by the join key is unrelated to the join type itself.