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.
正确答案:C,E
答案解析:有

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