The UNION ALL operator in SQL is used to combine the results of two or more SELECT statements:
Option D: It will return rows from both SELECT statements including duplicate rows.
UNION ALL does not eliminate duplicates; it simply combines all rows from the queries provided.
Options A, B, and C are incorrect as they describe behaviors of other set operators:
Option A: Describes the behavior of INTERSECT, not UNION ALL.
Option B: Describes the behavior of UNION, not UNION ALL.
Option C: Describes the behavior of EXCEPT or MINUS, not UNION ALL.