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单项选择题If a unique constraint is defined on column COL1 of table TAB1, what are the characteristics of COL1?（）

A、COL1 will accept NULL values and can be referenced in another table's foreign key specification.

B、COL1 will not accept NULL values and cannot be referenced in another tables foreign key specification.

C、COL1 will not accept NULL values and can be referenced in another tables foreign key specification.

D、COL1 will accept NULL values and cannot be referenced in another tables foreign key specification.

  • C

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