题目内容

当表中引入（）时，会提高记录的查询速度。

A. 外键
B. 主键
C. 索引
D. 数据库完整性

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在SQL中，可以使用（）语句执行恢复数据库的操作。

A. BACKUP DATABASE
B. RESTORE DATABASE
CREATE DARABASE
DROP DATABASE

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Directions:In this section, you will hear three news reports. At the end of each news report, you will hear two or three questions. Both the news report and the questions will be spoken only once. After you hear a question, you must choose the best answer from the four choices marked A), B), C) and D).Questions 1 and 2 are based on the news report you have just heard.[音频]1

A. Her grandfather.
B. Her grandmother
C. Her friend Erika.
D. Her little brother

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2

A. By taking pictures for passers-by.
By selling lemonade andpictures
C. By workingpart time at a hospital.
D. By asking for help on social media.

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Questions 3 and 4 are based on the news report you have just heard.[音频]3

A. Testing the efficiency of the new solar panel.
B. Providing clean energy to five million people.
C. Generating electric power for passing vehicles.
D. Finding cheaper ways of highway construction

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当表中引入（）时，会提高记录的查询速度。

A. 外键 B. 主键 C. 索引 D. 数据库完整性

在SQL中，可以使用（）语句执行恢复数据库的操作。

2

Questions 3 and 4 are based on the news report you have just heard.[音频]3

A. 外键
B. 主键
C. 索引
D. 数据库完整性