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- 1.以下哪条语句可以实现查询选了课的学生人数（ ）。 选项： A、select count(*) from sc B、select count(sno) from sc C、select count(distinct sno) from sc D、select count(cno) from sc
- 2.下列哪个语句可以查询选修了3门以上课程的学生学号选项： A:SELECT Sno FROM SC WHERE COUNT(Cno)>=3 B:SELECT Sno FROM SC GROUP BY Sno HAVING COUNT(Cno)>=3 C:SELECT Sno FROM SC GROUP BY Sno WHERE COUNT(Cno)>=3 D:SELECT Sno FROM SC GROUP BY Sno HAVING SUM(Cno)>=3
- 3.关系代数练习-学生选课（题干）.docx根据附件内容，查询已经选了课的学生人数。 选项：select COUNT(sNo) from SC;#select COUNT(*) from SC;#select COUNT(DISTINCT sNo) from SC;#select COUNT(DISTINCT *) from SC;
- 4.下列利用SC表的查询语句中，错误的是()选项： A:SELECT Sno, COUNT(*) FROM SC GROUP BY Sno; B:SELECT Sno FROM SC GROUP BY Sno HAVING COUNT(*) > 3; C:SELECT Sno FROM SC GROUP BY Sno WHERE COUNT(*) > 3; D:SELECT Sno FROM SC GROUP BY Sno
- 5.针对学生选课数据库S_T,以下哪条语句可以实现查询选了课的学生人数()。 选项： A、select count(distinct sno) from sc B、select count(*) fromsc C、select count(cno) fromsc D、select count(sno) from sc
- 6.针对学生选课数据库S_T,以下哪条语句可以实现查询选了课的学生人数( )。A.select count(distinct sno) from scB.select count(*) from scC.select count(cno) from scD.select count(sno) from sc
- 7.查询被选修过的课程数量，可以使用的查询语句是：（） 选项：SELECT COUNT(DISTINCT Cno) FROM SC;#SELECT AVG(DISTINCT *) FROM SC;#SELECT COUNT(ALL Cno) FROM SC;#SELECT COUNT(*) FROM SC;
- 8.查询被选修过的课程数量，可以使用的查询语句是： 。 选项：A、SELECT COUNT(DISTINCT Cno) FROM SC; B、SELECT AVG(DISTINCT *) FROM SC; C、SELECT COUNT(ALL Cno) FROM SC; D、SELECT COUNT(*) FROM SC;
- 9.【单选题】针对学生选课数据库S_T，以下哪条语句可以实现查询选了课的学生人数()。A. select count(cno) from scB. select count(sno) from scC. select count(*) from scD. select count(distinct sno) from sc
- 10.已知学生选课信息表：sc(sno,cno,grade)。查询“至少选修了一门课程，但没有学习成绩的学生学号和课程号”的SQL语句是（ ）。 选项： A:SELECT sno,cno FROM sc WHERE grade=NULL; B:SELECT sno,cno FROM sc WHERE grade IS '' ; C:SELECT sno,cno FROM sc WHERE grade IS NULL ; D:SELECT sno,cno FROM sc WHERE grade=''
- 11.已知学生选课信息表：sc(sno,cno,grade)。查询“至少选修了一门课程，但没有学习成绩的学生学号和课程号”的SQL语句是( )。选项： A:SELECT sno,cno FROM sc WHERE grade IS B:SELECT sno,cno FROM sc WHERE grade IS NULL C:SELECT sno,cno FROM sc WHERE grade=NULL D:SELECT sno,cno FROM sc WHERE grade=
- 12.在学生选课数据库中有学生表student(sno,sname,ssex,sage,sdept),课程表course(cno,cname)及学生选课表sc(sno,cno,grade),其中sno是学号,sname是姓名,ssex是性别,sage是年龄,sdept是系别,cno是课程号,cname是课程名,grade是成绩。以下哪条语句可以实现查询选了课的学生人数( )。A.select count(sno) from scB.select count(cno) from scC.select count(*) from scD.select count(distinct sno) from sc
- 13.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。 选项： 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')
- 14.针对学生选课表sc（sno, cno, grade），其中sno为学号，cno为课程号，grade为成绩。以下（ ）语句可查询选修了两门以上成绩在90分以上课程的学生学号。选项： A:select sno from scwhere grade>90group by snohaving count(cno)>2; B:select sno from scwhere grade>90group by snohaving count( distinct sno)>2; C:select sno from scwhere grade>90group by snohaving count(*)>2; D:select sno from scwhere grade>90 and count(*)>2group by sno
- 15.针对学生选课表sc（sno, cno, grade），其中sno为学号，cno为课程号，grade为成绩。以下（ ）语句可查询选修了两门以上成绩在90分以上课程的学生学号。选项： A:select sno from scwhere grade>90group by snohaving count(cno)>2; B:select sno from scwhere grade>90group by snohaving count( distinct sno)>2; C:select sno from scwhere grade>90group by snohaving count(*)>2; D:select sno from scwhere grade>90 and count(*)>2group by sno
- 16.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语句可以实现查询没有选修'C002'号课程的学生姓名。 A、 B、C、 D、 选项： A、SELECT SNAME FROM S, SC WHERE S.SNO=SC.SNO AND CNO !='C002' B、SELECT SNAME FROM S WHERE SNO NOT IN (SELECT SNO FROM SC WHERE CNO='C002') C、SELECT SNAME FROM S WHERE NOT EXISTS (SELECT * FROM SC WHERE S.SNO=SC.SNO AND CNO='C002') D、SELECT SNAME FROM S WHERE EXISTS (SELECT * FROM SC WHERE S.SNO=SC.SNO AND CNO !='C002')
- 17.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语句可以实现查询没有选修'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 NOT IN (SELECT SNO FROM SC WHERE CNO='C002')C.SELECT SNAME FROM S WHERE NOT EXISTS (SELECT * FROM SC WHERE S.SNO=SC.SNO AND CNO='C002')D.SELECT SNAME FROM S WHERE EXISTS (SELECT * FROM SC WHERE S.SNO=SC.SNO AND CNO !='C002')
- 18.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语句可以实现查询没有选修'C002'号课程的学生姓名。 选项： A、SELECT SNAME FROM S, SC WHERE S.SNO=SC.SNO AND CNO !='C002' B、SELECT SNAME FROM S WHERE SNO NOT IN (SELECT SNO FROM SC WHERE CNO='C002') C、SELECT SNAME FROM S WHERE NOT EXISTS (SELECT * FROM SC WHERE S.SNO=SC.SNO AND CNO='C002') D、SELECT SNAME FROM S WHERE EXISTS (SELECT * FROM SC WHERE S.SNO=SC.SNO AND CNO !='C002')
- 19.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语句可以实现查询没有选修'C002'号课程的学生姓名。选项： A:SELECT SNAME FROM S, SC WHERE S.SNO=SC.SNO AND CNO<>'C002'; B:SELECT SNAME FROM S WHERE SNO NOT IN (SELECT SNO FROM SC WHERE CNO='C002') ; C:SELECT SNAME FROM S WHERE SNO IN (SELECT SNO FROM SC WHERE CNO<>'C002') ; D:SELECT SNAME FROM S WHERE SNO = (SELECT SNO FROM SC WHERE CNO<>'C002')
- 20.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语句可以实现查询没有选修'C002'号课程的学生姓名。 选项： A、SELECT SNAME FROM S, SC WHERE S.SNO=SC.SNO AND CNO<;>;'C002' B、SELECT SNAME FROM S WHERE SNO NOT IN (SELECT SNO FROM SC WHERE CNO='C002') C、SELECT SNAME FROM S WHERE SNO IN (SELECT SNO FROM SC WHERE CNO<;>;'C002') D、SELECT SNAME FROM S WHERE SNO = (SELECT SNO FROM SC WHERE CNO<;>;'C002')
