默认题库 - 建设工程勘察设计、保修阶段质量管理

多选题

Which two statements are true about encrypting RMAN backup?（） (Choose two.)

A. The transparent encryption of backups uses the encryption wallet
B. The database uses the same encryption key for every encrypted backup
C. The password encryption of backups only uses the password while creating and restoring backup
D. If transparent encryption is configured, you cannot use the SET ENCRYPTION BY PASSWORD command to make password-protected backups.

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单选题

设两个关系中分别包括m和n个属性，它们具有同一个公共属性，当对它们进行自然连接，运算结果的关系中包括的属性个数为（）

A. m′n
B. m+n-1
C. m+n
D. m′n-1

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