第 65 题 (多选题)： Which three statements are true about inner and outer joins.

A. Outer joins can be used when there are multiple join conditions on two tables . B. Outer joins can only be used between two tables per query. C. A left or right outer join returns only unmatched rows. D. A full outer join returns matched and unmatched rows . E. An inner join returns matched rows. F. A full outer join must use Oracle syntax 显示答案