举一反三
- 有关系S(SNO, SNAME, SAGE),C(CNO, CNAME),SC(SNO, CNO, GRADE)。其中SNO是学生号,SNAME是学生姓名,SAGE是学生年龄, CNO是课程号,CNAME是课程名称,GRADE是成绩。以下( )SQL语句可以实现查询选修了'C002'号课程的学生姓名。 A: SELECT SNAME FROM S, SC WHERE S.SNO=SC.SNO AND CNO='C002' B: SELECT SNAME FROM S WHERE SNO IN (SELECT SNO FROM SC WHERE CNO='C002') C: SELECT SNAME FROM S WHERE SNO = (SELECT SNO FROM SC WHERE CNO='C002') D: SELECT SNAME FROM S WHERE SNO NOT IN (SELECT SNO FROM SC WHERE CNO='C002')
- 有关系S(S#,SNAME,SAGE),C(C#,CNAME),SC(S#,C#,GRADE)。若要查找分数(grade)不及格的学生姓名(sname),则以上正确的有?( ) A: SELECT sname FROM s, sc WHERE grade<60 B: SELECT sname FROM s WHERE sno IN(SELECT Cno FROM sc WHERE grade<60) C: SELECT sname FROM s, sc WHERE s.sno=sc.sno AND grade<60 D: SELECT sname FROM s, sc WHERE s.sno=sc.sno OR grade<60
- 有关系S(S#,SNAME,SAGE),C(C#,CNAME),SC(S#,C#,GRADE)。若要查找分数(grade)不及格的学生姓名(sname),则以上正确的有?( ) A: SELECT sname FROM s, sc WHERE grade<60 B: SELECT sname FROM s WHERE sno IN(SELECT Cno FROM sc WHERE grade<60) C: SELECT sname FROM s, sc WHERE s.sno=sc.sno AND grade<60 D: SELECT sname FROM s, sc WHERE s.sno=sc.sno OR grade<60
- 有如下的SQL语句.Ⅰ. SELECT sname FROM s, sc WHERE gradeⅡ. SELECT sname FROM s WHERE sno IN(SELECT sno FROM sc WHERE gradeⅢ. SELECT sname FROM s, sc WHERE s.sno=sc.sno AND grade若要查找分数(grade)不及格的学生姓名(sname),则以上正确的有哪些?( ) 。 A: Ⅰ和Ⅱ B: Ⅰ和Ⅲ C: Ⅱ和Ⅲ D: Ⅰ、Ⅱ和Ⅲ
- 第(23)~(24)题基于以下说明。设有三个关系: 学生关系S(SNO,SNAME,AGE,SEX)(分别代表学生的学号、姓名、年龄、性别) 学习关系SC(SNO,CNO,GRADE)(分别代表学生的学号、课程编号、成绩) 课程关系C(CNO,CNAME,TEACHER)(分别代表课程的编号、课程名、任课教师) 检索“至少选修课程号为’C1’的学生姓名(SNAME)”的SQL语句是 A: SELECT s. sname FROM s, sc WHERE c. cno=’C1’ B: SELECT s. sname FROM s, sc WHERE c. cno=’C1’AND s. sno=sc. sno C: SELECT s. sname FROM s, sc FOR c. cno=’C1’ D: SELECT s. sname FROM s, sc FOR c. cno=’C1’ AND s. sno=sc. sno
内容
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有如下的SQL语句:Ⅰ. SELECT sname FROM s, sc WHERE grade<;60Ⅱ. SELECT sname FROM s WHERE sno IN(SELECT sno FROM sc WHERE grade<;60)Ⅲ. SELECT sname FROM s, sc WHERE s.sno=sc.sno AND grade<;60若要查找分数(grade)不及格的学生姓名(sname),则以上正确的有哪些?() A: Ⅰ和Ⅱ B: Ⅰ和Ⅲ C: Ⅱ和Ⅲ D: Ⅰ、Ⅱ和Ⅲ
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有如下的SQL语句: Ⅰ.SELECT sname FROM s, sc WHERE grade<60 Ⅱ.SELECT sname FROM s WHERE sno IN(SELECT sno FROM sc WHERE grade<60) Ⅲ.SELECT sname FROM s, sc WHERE s.sno=sc.sno AND grade<60 若要查找分数(grade)不及格的学生姓名(sname),则以上正确的有哪些?( ) A: Ⅰ和Ⅱ B: Ⅰ和Ⅲ C: Ⅱ和Ⅲ D: Ⅰ、Ⅱ和Ⅲ
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在学生选课数据库中,检索被全部学生所选修的课程的SQL可以描述为( ) A: SELECT Cno FROM SC WHERE (Select Count(Sno) FROM SC GROUP BY Cno) = (SELECT Count(*) FROM Student) ; B: SELECT Cno FROM SC x WHERE NOT EXISTS (SELECT * FROM Student s WHERE NOT EXISTS (SELECT * FROM SC y WHERE x.Cno = y.Cno AND s.Sno= y.Sno); C: SELECT Cno FROM SC x WHERE NOT EXISTS (( SELECT Sno FROM Student) EXCEPT ( SELECT y.Sno FROM SC y, Student z WHERE x.Cno=y.Cno AND z.Sno=y.Sno)); D: 以上答案都不对
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在学生选课数据库中,查询选修了课程的学生的学号、姓名,SQL语句可为( ) A: SELECT DISTINCT Sno, Sname FROM Student, SC WHERE Student.Sno = SC.Sno; B: SELECT Sno, Sname FROM Student, SC WHERE Student.Sno = SC.Sno; C: SELECT DISTINCT Sno, DISTINCT Sname FROM Student WHERE Student.Sno IN (SELECT Sno FROM SC); D: SELECT Sno, Sname FROM Student WHERE Student.Sno IN (SELECT DISTINCT Sno FROM SC);
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23~24 题基于以下说明。设有三个关系 学生关系S(SNO,SNAME,AGE,SEX) (分别代表学生的学号、姓名、年龄、性别) 学习关系SC(SNO,CNO,GRADE) (分别代表学生的学号、课程编号、成绩) 课程关系C(CNO,CNAME,TEACHER) (分别代表课程的编号、课程名、任课教师) 检索“至少选修课程号为′C1′的学生姓名(SNAME) ”的SQL语句是 A: SELECT s.sname FROM s,sc WHERE c.cno=′C1′ B: SELECT s.sname FROM s,sc WHERE c.cno=′C1′AND s.sno=sc.sno C: SELECT s.sname FROM s,sc FOR c.cno=′C1′ D: SELECT s.sname FROM s,sc FOR c.cno=′C1′AND s.sno=sc.sno