In which two cases would you use an outer join?（）

• A、The tables being joined have NOT NULL columns.
• B、The tables being joined have only matched data.
• C、The columns being joined have NULL values.
• D、The tables being joined have only unmatched data.
• E、The tables being joined have both matched and unmatched data.
• F、Only when the tables have a primary key/foreign key relationship.