问题 单项选择题

设有学生实体Students(学号,姓名,性别,年龄,家庭住址,家庭成员,关系,联系电话),其中“家庭住址”记录了邮编、省、市、街道信息;“家庭成员,关系,联系电话”分别记录了学生亲属的姓名、与学生的关系以及联系电话。学生实体Students中的“家庭住址”是一个(49)属性;为使数据库模式设计更合理,对于关系模式Students(50)。空白(49)处应选择()

A.简单

B.多值

C.派生

D.复合

答案

参考答案:D

解析:这两题考查数据库基本概念和数据库设计的基本知识。(49)复合属性是多个简单属性的复合,多值属性是包含多个属性相同的值的属性。

单项选择题
单项选择题

Lying in the sun on a rock, the cougar(美洲狮) saw Jeb and his son, Tom, before they saw it. Jeb put his bag down quickly and pulled his jacket open with both hands, making himself look big to the cougar. It worked. The cougar hesitated, ready to attack Jeb, but ready to forget the whole thing, too.

Jeb took off his jacket, grasped Tom and held him across his body, making a cross. Now the cougar’ s enemy looked even bigger, and it rose up, ready to move away, but unfortunately Tom got scared and struggled free of Jeb.

"Tom, No !" shouted his father.

But Tom broke and ran and that’ s the last thing you do with a cougar. The second Tom broke free, Jeb threw himself on the cougar, just as it jumped from the rock. They hit each other in mid-air and both fell. The cougar was on Jeb in a flash, forgetting about Tom, which was what Jeb wanted. Cougars are not as big as most people think and a determined man stands a chance, even with just his fists. As the cougar’s claws got into his left shoulder, Jeb swung his fist at its eyes and hit hard. The animal howled(吼叫)and put its head back. Jeb followed up with his other fist. Then out of the comer of his eye, Jeb saw Tom. The boy was running back to help his father.

"Knife, Tom," shouted Jeb.

The boy ran to his father’ s bag, while Jeb started shouting as well as hitting, to keep the cou-gar’s attention away from Tom. Tom got the knife and ran over to Jeb. The cougar was moving its head in and out, trying to find a way through the wall. Jeb was making out of his arms. Tom swung with the knife, into the cougar’ s back. It howled horribly and ran off into the mountains.

Which of the following happened first()

A. The cougar jumped from the rock.

B. Tom struggled free of his father.

C. Jeb asked Tom to get the knife.

D. Jeb held Tom across his body.