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单选题
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.


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