举一反三
- 下列SQL语句中，_____________可以在“学生-课程”数据库正确实现“计算1号课程的学生平均成绩”。 A: SELECT AVG(Grade)FROM SCWHERE Cno= ' 1 ' B: SELECT MAX(Grade)FROM SCWHERE Cno= 1 C: SELECT MIN(Grade)FROM SCWHERE Cno= 1 D: SELECT AVG(Grade)FROM SCWHERE Cno= 1
- 检索选修了课程”C1”的学生中成绩最高的学生的学号，正确的SELECT语句为（ ） A: SELECT Sno FROM SC WHERE Cno=’C1’ AND GRADE >=ALL (SELECT Grade FROM SC WHERE Cno=’C1’); B: SELECT Sno FROM SC WHERE Cno=’C1’ AND GRADE IN (SELECT Grade FROM SC WHERE Cno=’C1’); C: SELECT Sno FROM SC WHERE Cno=’C1’ AND GRADE > ANY (SELECT Grade FROM SC WHERE Cno=’C1’); D: SELECT Sno FROM SC WHERE Cno=’C1’ AND GRADE >= (SELECT Grade FROM SC WHERE Cno=’C1’);
- 检索选修课程“C2”的学生中成绩最高的学生的学号。正确的SELECT语句是（）。 A: SELECT SNO FROM SC WHERE CNO='C2' AND GRADE >= ( SELECT GRADE FORM SC WHERE CNO='C2' ); B: SELECT SNO FROM SC WHERE CNO='C2' AND GRADE IN ( SELECT GRADE FORM SC WHERE CNO='C2' ); C: SELECT SNO FROM SC WHERE CNO='C2' AND GRADE NOT IN ( SELECT GRADE FORM SC WHERE CNO='C2' ); D: SELECT SNO FROM SC WHERE CNO='C2' AND GRADE >= ALL ( SELECT GRADE FORM SC WHERE CNO='C2' );
- 查询选修了数学课(课程号为2)的学生人数,可以使用的查询语句是: 。 A: SELECT MAX(*) FROM SC WHERE Cno = 2; B: SELECT AVG(Sno) FROM SC WHERE Cno = 2; C: SELECT COUNT(*) FROM SC WHERE Cno = 2; D: SELECT COUNT(Sname) FROM SC WHERE Cno = 2;
- 统计选修了a001课程的学生的平均成绩( ) A: select cid,avg(grade) from student group by cid having cid=’a001’ B: select cid,avg(grade) from student where cid=’a001’ group by cid C: select cid,avg(grade) from course where cid=’a001’ group by cid D: select cid,avg(grade) from sc where cid=’a001’ group by cid
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下列SQL语句中，_____________可以在“学生-课程”数据库正确实现“找出每个学生超过他选修课程平均成绩的课程号”。 A: SELECT Sno，CnoFROM SC xWHERE Grade >=(SELECT AVG(Grade) FROM SC y WHERE y.Sno=x.Sno) B: SELECT Sno，CnoFROM SC xWHERE (SELECT AVG(Grade) FROM SC y WHERE y.Sno=x.Sno)<=Grade C: SELECT Sno，CnoFROM SC WHERE Grade >=(SELECT AVG(Grade) FROM SC ) D: SELECT x.Sno，x.CnoFROM SC x, SC yWHERE y.Sno=x.Sno AND x.Grade >=(SELECT AVG(Grade) FROM y)
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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（ ）。 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=
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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。 A: select sno from scwhere grade>90group by snohaving count(cno)>2 B: select sno from scwhere grade>90group by snohaving count(*)>2 C: select sno from scwhere grade>90 and count(*)>2group by sno D: select sno from scwhere grade>90group by snohaving count(sno)>2
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有学生表S(S#,SN,SEX,AGE,DEPT),课程表C(C#,CN),学生选课表SC(S#,C#,GRADE),检索选修课程"C2"的学生中成绩最高的学生的学号,正确的SELECT语句是_________。 A: SELECT S# FROM SCWHERE C#="C2" AND GRADE>=(SELECT GRADE FROM SC WHERE C#="C2") B: SELECT S# FROM SCWHERE C#="C2" AND GRADE IN(SELECT GRADE FROM SC WHERE C#="C2") C: SELECT S# FROM SCWHERE C#="C2" AND GRADE NOT IN(SELECT GRADE FROM SC WHERE C#="C2") D: SELECT S# FROM SCWHERE C#="C2" AND GRADE>=ALL
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按照课程号进行分组，统计学生平均成绩大于60分的学生的信息( ) A: select cid,avg(grade) from sc group by cid having avg(grade)>60 B: select cid,avg(grade) from student group by cid having avg(grade)>60 C: select cid,avg(grade) from course where avg(grade)>60 group by cid D: select cid,avg(grade) from student where avg(grade)>60 group by cid