问题 单项选择题

关系数据库的数据及更新操作必须遵循的完整性规则是( )。

A) 实体完整性和参照完整性
B) 参照完整性和用户定义的完整性
C) 实体完整性和用户定义的完整性
D) 实体完整性、参照完整性和用户定义的完整性

答案

参考答案:A

解析: 本题考核数据的完整性。关系模型允许定义3类数据的约束,他们是实体完整性约束、参照完整性约束以及用户自定义完整性约束。其中实体完整性和参照完整性是关系数据库的数据及更新操作必须遵循的完整性规则,在任何一个关系数据库管理系统中均由系统自动支持。

阅读理解

阅读理解。

     There was a story many years ago of a school teacher-Mrs. Thompson. She told the children on the first

day that she loved them all the same. But that was a lie. There in the front row was a little boy named Teddy

Stoddard. He didn't play well with the other children and he always needed a bath. She did not like him.

     Then Mrs. Thompson got to know that Teddy was actually a very good boy before the death of his mother.

Mrs. Thompson was ashamed of herself. She felt even worse when, like all her other students, Teddy brought

her a Christmas present too. It was his mother's perfume (香水).

     Teddy said, "Mrs. Thompson, today you smell just like my Mom used to." After the children left she cried

for at least an hour. On that very day, she stopped teaching reading, writing and math. Instead, she began to

teach children.

     Mrs. Thompson paid particular attention to Teddy. The boy's mind seemed to come alive. The more she

encourages him, the faster he improved. By the end of the sixth grade, Teddy had become one of the smartest

children in the class.

     Six years went by before she got a note from Teddy. He wrote that he had finished high school, third in his

class, and she was still the best teacher he ever had in his whole lift. He went to college. Mrs. Thompson got

two more letters from him with the last one signed, Theodore F. Stoddard, M.D. (医学博士). 

     The story doesn't end there. On his wedding day, Dr. Stoddard whispered in Mrs. Thompson's ear, "Thank

you, Mrs. Thompson, for believing in me. You made me feel important and showed me that I could make a

difference."

     Mrs. Thompson, with tears in her eyes, whispered back, "Teddy, you have it all wrong. You were the one

who taught me that I could make a difference. I didn't know how to teach until I met you."

1. What did Mrs. Thompson do on the first day of school?

A. She made Teddy feel ashamed.

B. She asked the children to play with Teddy.

C. She changed Teddy's seat to the front row.

D. She told the class something untrue about herself.

2. What did Mrs. Thompson find out about Teddy?

A. He often told lies.

B. He was good at math.

C. He needed motherly care.

D. He enjoyed playing with others.

3. In what way did Mrs. Thompson change?

A. She taught fewer school subjects.

B. She became stricter with her students.

C. She no longer liked her job as a teacher.

D. She cared more about educating students.

4. Why did Teddy thank Mrs. Thompson at his wedding?

A. She had kept in touch with him.

B. She had given him encouragement.

C. She had sent him Christmas presents.

D. She had taught him how to judge people.

多项选择题