问题 填空题

在关系模型中,二维表的行称为______。

答案

参考答案:元组

解析: 在关系型数据库中,用二维表来表示关系,二维表的表名即关系名,二维表的行称为关系的元组,二维表的列称为关系的属性。

阅读理解

Here is some information about homes in the United States and the people who live in them.

In the early 1990s, there were more than 91 million homes, or households(家庭) in the US. About 64% of the people in the US own their homes. The rest(其余的) rent(租) their homes. The rented homes are usually apartments(公寓).

74%of the people in the US make their homes in or around cities. 26% live in the country(乡下). Dogs live in about 40% of all homes in the US and about half that number have cats.

Families in the US are becoming smaller. On the average(平均), 2.64 people lived in a home in the early 1990s. In 1960, the average was 3.5.

Half of the teenagers (青少年) in the US have their own bedrooms.

An American moves(搬家), on the average, twelve times in his or her life. In Japan a person moves about five times, and in England a person moves eight times.

小题1:Where do most Americans live?

A.Around the country.

B.In or around cities.

C.In the country.

D.In cities.小题2:How many American families own a cat?

A.40%

B.64%

C.20%

D.74%小题3:Families in the US are      .

A.becoming bigger .

B.becoming smaller

C.becoming happy.

D.not sure小题4:Which of the following is TURE?

A.Americans move more often than the English.

B.The average number in a family now is getting bigger than that in the 1960s.

C.The Japanese move . more often than the British.

D.Most young people of the US have no bedrooms of their own.小题5:The best title for the passage is about       .

A.Americans moving homes all the time

B.Pets in American families.

C.City families & country families.

D.Americans families.

问答题

某水利枢纽工程由电站、溢洪道和土坝组成。主坝为均质土坝,上游设干砌石护坡,下游设草皮护坡和堆石排水体,坝顶设碎石路,工程实施过程中发生下述事件:
事件1:项目法人委托该工程质量监督机构对于大坝填筑按《水利水电基本建设工程单元工程质量评定标准》规定的检验数量进行质量检查。质量监督机构受项目法人委托,承担了该工程质量检测任务。
事件2:土坝施工单位将坝体碾压分包给具有良好碾压设备和经验的乙公司承担。合同文件中,单元工程的划分标准是:以40m坝长、20cm铺料厚度为单元工程的计算单位,铺料为一个单元工程,碾压为另一个单元工程。
事件3:该工程监理单位给施工单位“监理通知”如下:经你单位申请并提出设计变更,我单位复核同意将坝下游排水体改为浆砌石,边坡由1:2.5改为1:2。
事件4:土坝单位工程完工验收结论为:本单位工程划分为30个分部工程,其中质量合格12个,质量优良18个,优良率为60%,主要分部工程(坝顶碎石路)质量优良,且施工中未发生重大质量事故;中间产品质量全部合格,其中混凝土拌合物质量达到优良;原材料质量、金属结构及启闭机制造质量合格;外观质量得分率为83%。所以,本单位工程质量评定为优良。
事件5:该工程项目单元工程质量评定表由监理单位填写,土坝单位工程完工验收由施工单位主持。工程截流验收及移民安置验收由项目法人主持。
问题:

土坝单位工程质量等级实际为优良。依据水利工程验收和质量评定的有关规定,简要分析事件4中验收结论存在的问题。