问题 单项选择题

建立一个供应商、零件数据库。其中“供应商”表S(Sno,Sname,Zip,City)分别表示:供应商代码、供应商名、供应商邮编、供应商所在城市,其函数依赖为:Sno→(Sname,Zip,City),Zip→City。“供应商”表S属于()。

A.3NF

B.BCNF

C.1NF

D.2NF

答案

参考答案:D

解析:

[要点解析] 本题考查的是范式的基础知识。“供应商”表S属于2NF,因为表S的主键是 Sno,非主属性Sname、Zip、City不存在对键的部分函数依赖。但是,当2NF消除了非主属性对码的传递函数依赖,则称为3NF。“供应商”表S不属于3NF,因为存在传递依赖,即Sno→Zip,Zip→City。所以正确答案是B。

完形填空
完形填空。

       Tony is a successful businessman. He ever used to have a happy family. But three years ago, his wife
  1   because of illness.  He loves his daughter very much, so he hasn't   2   again. He is still alone.    
       Today is his  3   birthday. He wants to cheer her up, so he decided to have a birthday party specially
for her in their house. In the morning, he cleaned up all rooms. After lunch, he drove his car to buy some
fresh flowers and fruits and a big cake.   4   his way home, he noticed an _5    man whose wheelchair was
broken. He stopped his car on   6   side of the street, then he walked to him and helped him   7   the
wheelchair. After he finished it, he drove home quickly.    
       After he got home, he put the purple flowers in her daughter's bedroom. Then he set the fruits, the cake, and some forks on the table. He   8   wanted to make some delicious pies for the guests. By the time
someone   9   at the door, he had prepared all things well. He gave his daughter a   10   birthdayparty.

( )1. A. dead        
( )2. A. married      
( )3. A. son's        
( )4. A. In          
( )5. A. blind        
( )6. A. other        
( )7. A. repair      
( )8. A. too          
( )9. A. went        
( )10. A. exciting    
B. died      
B. worked    
B. daughter's
B. For      
B. deaf      
B. both      
B. push      
B. as well  
B. put      
B. surprised
C. death        
C. had a job    
C. wife's        
C. At            
C. disabled      
C. another      
C. pull          
C. either        
C. turned        
C. interesting  
D. has been dead        
D. spoken                
D. friend's              
D. On                    
D. blind and deaf        
D. either                
D. carry                
D. also                  
D. knocked              
D. surprising            
名词解释