What is true of using group functions on columns that contain NULL values?（）
- A、Group functions on columns ignore NULL values.
- B、Group functions on columns returning dates include NULL values.
- C、Group functions on columns returning numbers include NULL values.
- D、Group functions on columns cannot be accurately used on columns that contain NULL values.
- E、Group functions on columns include NULL values in calculations if you use the keyword INC_NULLS.
正确答案:A
答案解析:有
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