当前位置:考试网  > 试卷库  > 学历类  > 自考  > 自考专业(电子商务)  > 互联网数据库  >  已知某个研究所中有多个科室,每个科室有多个职员,每个职员只在一个科室中,每个职员参加多种项目的研发,而每种项目的研发可由多个职员参加。 科室:科室编号,科室名; 职员:工号,职员名,出生日期; 项目:项目号,项目名称,开始日期。 每个职员参加某个项目,都有参加该项目的时间。 请根据上述语义完成以下操作: (1)建立一个反映上述局部应用的ER模型,要求标注联系类型(可省略实体属性)。 (2)将ER模型转换为关系模型,要求标注每个关系模型的主键和外键(如果存在)。
试题预览

已知某个研究所中有多个科室,每个科室有多个职员,每个职员只在一个科室中,每个职员参加多种项目的研发,而每种项目的研发可由多个职员参加。

科室:科室编号,科室名;

职员:工号,职员名,出生日期;

项目:项目号,项目名称,开始日期。

每个职员参加某个项目,都有参加该项目的时间。

请根据上述语义完成以下操作:

(1)建立一个反映上述局部应用的ER模型,要求标注联系类型(可省略实体属性)。

(2)将ER模型转换为关系模型,要求标注每个关系模型的主键和外键(如果存在)。

查看答案
收藏
纠错
正确答案:

1

答案解析:

暂无解析

你可能感兴趣的试题

下列关于JDBC的叙述中,错误的是()

由并发操作引起的数据不一致性包括丢失修改、不能重复读和_____。

在JDBC中,充当可移植的接口并且是指向所有驱动程序的入口点的类是_____类。

成员Java.sql.DriverPropertyInfo属于JDBC中的()

简述数据库管理系统完整性控制机制应具有的功能。

热门试题 更多>
试题分类: 社区工作人员
练习次数:0次
Questions 1 to 5 are based on the following passage: Some years ago the captain of a ship was very interested in medicine. He always took medicine books to sea and liked to talk about different diseases. One day a lazy sailor on his ship pretended to be ill. He lay on his bunk (铺) and groaned as if he were very sick. The captain came to see him and was very pleased to have a patient to look after. He told the man to rest for a few days and made the other sailors do his work. Three days later another sailor pretended that he had something wrong with his chest. Once more the captain looked in his medical books and told “sick” man to have a rest. The other sailors were very angry because they had more work to do. The patients had the best food and laughed at their friends when the captain was not looking. At last the mate (船长副手) decided to cure the “sick” men. He mixed up some soap, soot (烟灰), glue (胶水) and other unpleasant things. Then he obtained permission from the captain to give his medicine to the “sick” men. When they tasted the medicine, they really did feel ill. It was so horrible that one of the patients jumped out of hi bunk, ran up on desk and climbed the highest mast on the ship. He did not want any more medicine. The mate told both of the men that they must take the medicine every half an hour, night and day. This soon cured them. They both said they felt better and wanted to start word again. The captain realized that the men tried to deceive him so he made them work very hard for the rest of the voyage. 1. The first sailor pretended to be ill because he wanted to . A. test the captain’s knowledge of medicine  B. be free from work C. have the best food on the ship  D. play a joke on his friends 2. When the captain knew a sailor was ill, he . A. didn’t care much  B. sent for a doctor C. looked after him and told him to have a rest D. gave him some medicine 3. The patients felt better quickly because . A. they had been given proper medicine B. they learned that the captain had found out the truth C. they were laughed at by their friends D. the medicine the mate gave was horrible 4. When the captain knew he had been deceived, he . A. told them not to do so again  B. lost his temper C. made them work harder  D. fired them 5. Which of the following best summarizes the passage? A. A sudden Cure.  B. Two Patients.  C. Captain and Sailors.  D. A Difficult Voyage.
试题分类: 大学英语六级
练习次数:0次
Part III Cloze Directions: There are twenty blanks in the following passage. For each blank there are four choices. Choose the one that best fits into the passage and then marks your answer on the Answer Sheet. There are two factors which determine an individual’s intelligence. The first is the sort of brain he is born 61 . Human brains differ considerably, 62 being more capable than others. 63 no matter how good a brain he has to begin with, an individual will have a low order of intelligence 64 he has opportunities to learn. So the second factor is what 65 to the individual—the sort of environment in which he is brought 66 . If an individual is handicapped (受阻碍) 67 , it is likely that his brain will 68 to develop and he will 69 attain the level of intelligence of which he is 70 . The importance of environment in determining an individual’s intelligence can be 71 by the case history of the identical twins, Peter and John. When the twins were three months old, their parents died, and they are placed in 72 foster (寄养) homes. Peter was reared by parents of low intelligence in an 73 community with poor educational 74 . John, 75 , was educated in the home of well-to-do parents who has been to college. This environmental 76 continued until the twins were 77 their late teens, 78 they were given tests to 79 their intelligence. John’s I.Q. (智商) was 125, twenty-five points higher than the 80 and fully forty points higher than his identical brother. 61. A. for B. by C. with D. in 62. A. most B. some C. many D. few 63. A. But B. For C. Still D. And 64. A. if B. thought C. as D. unless 65. A. refers B. applies C. happens D. concerns 66. A. about B. up C. forward D. forth 67. A. relatively B. intelligently C. regularly D. environmentally 68. A. fail B. help C. manage D. stop 69. A. ever B. never C. even D. nearly 70. A. able B. capable C. available D. acceptable 71. A. demonstrated B. denied C. neglected D. ignored 72. A. separate B. similar C. remote D. individual 73. A. omitted B. isolated C. enclosed D. occupied 74. A. possibilities B. opportunities C. capacities D. responsibilities 75. A. moreover B. consequently C. then D. however 76. A. exception B. division C. difference D. alteration 77. A. in B. by C. at C. for 78. A. while B. since C. when D. because 79. A. estimate B. count C. decide D. measure 80. A. average B. common C. usual D. ordinary
试题分类: 大学英语四级
练习次数:0次
背景资料: A施工单位总包一炼钢厂项目,其中的连铸安装工程分包B 安装公司,该公司及时组建了项目部,项目部在组 织施工过程中发生以下情况: 情况一:项目部按工业安装工程质量验评项目划分规定对安装工程项目进行了划分,其中有连铸安装工程、机械设备安装工程、蒸汽排除风机安装工程、电气安装工程、自动化仪表安装工程等。 情况二:在自动化仪表工程施工完毕后,进行了综合控制系统试验,然后编制竣工资料,准备交工验收。 情况三:项目部安装完成后,向建设单位要求办理交工验收手续,建设单位以不符合工程验收的规定而拒绝了项目部的要求。 情况四:施工合同按《建设工程质量管理条例》规定签订了在正常使用条件下的最低保修期限。 该工程生产线在正常运行4 年后,因设备故障、电气管线故障、给排水管网阀门漏水、中央控制室的供热和供冷系统失效而导致停产。建设单位发函要求该施工单位进行保修。施工单位以超过了保修期婉拒建设单位的要求。 问题: 1. 按质量验评标准规定,指出情况一中所列项目哪些属单位工程?哪些属分部工程和分项工程? 2. 情况二中,自动化仪表在综合控制系统试验后编制竣工资料,准备交工验收是否正确?为什么? 3. 该工程验收必须符合哪些规定? 4. 该工程中设备安装、电气管线、给水排水管道、供热和供冷系统的最低保修期限是多少?
试题分类: 安全员
练习次数:0次
扫一扫,手机做题