【简答题】( 6 ) 检索年龄大于 21 的男学生学号和姓名。 ( 7 ) 检索 第 2学期开设的 课程的名 称和学分 。 ( 8 ) 检索 ””同学不学课程的课程号。 ( 9 ) 检索至少选修两门课程的学生学号。 ( 10 ) 检索全部学生都选修的课程的课程号和课程名。
【单选题】检索全部学生都选修的课程的课程号和课程名。
A.
∏sno,cno,cname(C∞SC)÷∏sno(S)
B.
∏cno,cname(C∞SC)÷∏sno(S)
D.
∏sno,cno,cname(C∞SC)÷∏sno(SC)
【简答题】根据标的物不同,招标发行可分为( )。 A美国式招标 B收益率招标 C缴款期招标 D价格招标
【单选题】The wild mouflon sheep of the island of Corsica are direct descendants of sheep that escaped from domestication on the island 8,000 years ago. They therefore provide archaeologists with a picture of w...
A.
The domesticated sheep of 8,000 years ago were quite dissimilar from the wild sheep of the time.
B.
There are no other existing breeds of sheep that escaped from domestication at about the same time as the forebears of the mouflon.
C.
Modern domesticated sheep are direct descendants of sheep that were wild 8,000 years ago.
D.
Mouflon sheep are more similar to their forebears of 8,000 years ago than modern domesticated sheep are to theirs.
E.
The climate of Corsica has not changed at all in the last 8,000 years.
【单选题】Somehow the sheep jumped ___ the fence.
【简答题】设教学数据库中有4个关系:教师关系T(T#,TNAME,TITLE)课程关系C(C#,CNAME,T#)学生关系S(S#,SNAME,AGE,)选课关系SC(S#,C#,SCORE)试用关系代数表达式表示各个查询语句。(1)检索年龄小于17岁的女学生的学号和姓名。(2)检索男学生所学课程的课程号和课程名。(3)检索男学生所学课程的任课老师的职工号和姓名。(4)检索至少选修了两门课程的学生学号...
【单选题】开放者花冠筒状,先端二唇形;雄蕊5枚,附于筒壁,黄色;雌蕊1枚,子房。是以下哪种药材的性状鉴别()