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使用如下三个数据库表：学生(学号C(8)，姓名C(8)，性别C(2)，班级C(8)) 课程(课程编号C(8)，课程名称C(20)) 成绩(学号C(8)，课程编号C(8)，成绩N(5，1)) 检索还未确定成绩的学生选课信息，正确的SQL命令是

A. SELECT 学生.学号，姓名，成绩.课程编号 FROM 学生 JOIN 成绩
B. WHERE 学生，学号=成绩，学号 AND 成绩，成绩 IS NULL
C. SELECT 学生.学号，姓名，成绩.课程编号 FROM 学生 JOIN 成绩
D. WHERE 学生.学号=成绩.学号 AND 成绩.成绩=NULL
E. SELECT 学生.学号，姓名，成绩.课程编号 FROM 学生 JOIN 成绩
F. ON 学生.学号=成绩，学号 WHERE 成绩，成绩 IS NULL
G. SELECT 学生.学号，姓名，成绩，课程编号 FROM 学生 JOIN 成绩
H. ON 学生，学号=成绩，学号 WHERE 成绩.成绩=NULL

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使用如下三个数据库表：学生(学号C(8)，姓名C(8)，性别C(2)，班级C(8)) 课程(课程编号C(8)，课程名称C(20)) 成绩(学号C(8)，课程编号C(8)，成绩N(5，1)) 查询所有选修了“高等数学”的学生的“高等数学”成绩，要求得到的信息包括学生姓名和成绩，并按成绩由低到高的顺序排列，下列语句正确的是

A. SELECT 学生.姓名，成绩.成绩 FROM 学生，成绩；
B. WHERE 学生.学号=成绩.学号；AND 课程.课程名称=’高等数学’；
C. ORDER BY 成绩.成绩 ASC
D. SELECT 学生，姓名，成绩.成绩 FROM 课程，成绩；
E. WHERE AND 课程.课程编号=成绩.课程编号；AND 课程.课程名称=’高等数学’；
F. ORDER BY 成绩.成绩 ASC
G. SELECT 学生.姓名，成绩.成绩 FROM 学生，课程，成绩；
H. WHERE 学生.学号=成绩.学号；AND 课程.课程编号=成绩.课程编号；AND课程.课程名称=’高等数学’；
I. GROUP BY 成绩，成绩 ASC
J. SELECT 学生.姓名，成绩.成绩 FROM 学生，课程，成绩；
K. WHERE 学生.学号=成绩.学号；AND 课程.课程编号=成绩.课程编号；AND 课程.课程名称=’高等数学’；
L. ORDER BY 成绩.成绩 ASC

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概念模型的表示方法最常用的是______，这是P.P.S.Shen于1976年提出的。

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数据字典的实现可以有3种途径：人工过程、自动化过程和______。

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More than seven hundred years ago, the Prince of Wales had a very big and brave dog, Gelert. One day the Prince wanted to go hunting with his men. He told his dog to stay at home and look after his baby son. The baby was in a wooden cradle, which was like a small bed.When the Prince came back from hunting, Gelert ran out to meet his master. Then the Prince saw blood on Gelert’s jaws and head."What have you done" The Prince said. He rushed into his home and looked for his baby son. The cradle was lying on its side on the floor. The clothes were torn and there was blood on them."So you killed my son!" the Prince said angrily. "You unfaithful dog!" He took out his sword and killed the dog. Just as Gelert was dying, he managed to bark for a moment. Then the Prince heard a baby call to the dog.The Prince ran out of the house and saw his son lying on the ground unhurt. Near him was a dead wolf. Then the Prince knew that Gelert had defended the baby and killed the wolf.The Prince ran back into the house but he was too late. Gelert was dead. The Prince was very sad indeed. Tears ran down his face when he realized he had killed his faithful friend. After this, the Prince never smiled again. Every morning at dawn, he walked up the mountain so that he could stand by the dog’s grave for a few minutes. Whose dog was Gelert().

A. Of the Prince of Scotland.
B. Of the Prince of England.
C. Of the Prince of Ireland.
D. Of the Prince of Wales.

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使用如下三个数据库表： 学生(学号C(8)，姓名C(8)，性别C(2)，班级C(8)) 课程(课程编号C(8)，课程名称C(20)) 成绩(学号C(8)，课程编号C(8)，成绩N(5，1)) 检索还未确定成绩的学生选课信息，正确的SQL命令是

概念模型的表示方法最常用的是______，这是P.P.S.Shen于1976年提出的。

数据字典的实现可以有3种途径：人工过程、自动化过程和______。

使用如下三个数据库表：学生(学号C(8)，姓名C(8)，性别C(2)，班级C(8)) 课程(课程编号C(8)，课程名称C(20)) 成绩(学号C(8)，课程编号C(8)，成绩N(5，1)) 检索还未确定成绩的学生选课信息，正确的SQL命令是