问题
单项选择题
在创建数据库表结构时，为该表中一些字段建立普通索引，其目的是( )。
A) 改变表中记录的物理顺序
B) 为了对表进行实体完整性约束
C) 加快数据库表的更新速度
D) 加快数据库表的查询速度
答案
参考答案：D
解析： 建立索引，可以加快数据表的查询速度，不会改变表中的物理顺序。
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在创建数据库表结构时，为该表中一些字段建立普通索引，其目的是( )。
A) 改变表中记录的物理顺序
B) 为了对表进行实体完整性约束
C) 加快数据库表的更新速度
D) 加快数据库表的查询速度
参考答案：D
解析： 建立索引，可以加快数据表的查询速度，不会改变表中的物理顺序。
The telephone rang in the police station at Richmond, California, US. “ station? A train for Santa Fe collided (相撞) a at the McDonald Street Crossing. Please come here at once. With an ambulance, too. A man is badly wounded,” said an anxious voice of a young woman. “OK. We’ll come soon. Please stay there and wait.” Replied the policeman. Within a minute, a police car and an ambulance off. Soon they got to the crossing, but only to find everything was fine. No collision, no wounded man. “What a dirty !” said the policeman angrily. “ We must find out that woman and…” They had not been able to say anything about a when they heard the whistle of a train was nearing them quickly. All of a sudden, a truck appeared. It came towards them, too. When it was passing the crossing, it suddenly to move on. Right then and there, before the eyes of all the people present, the train collided with the truck heavily and struck it dozens of metres away. When Randolph Bruce, the driver, was helped out of the damaged truck, he was badly wounded just as the young woman had predicted on the phone. As he was taken to hospital in time, he was at last. Later the police did whatever they could to the woman who had them, but failed. It is really that a prediction should agree with the fact so .
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