• 2022-06-19
    下列查询语句中,错误的是()。
    A: SELECT Sno, COUNT(*) FROM SC GROUP BY Sno
    B: SELECT Sno FROM SC GROUP BY Sno WHERE COUNT(*)> 3
    C: SELECT Sno FROM SC GROUP BY Sno HAVING COUNT(*)> 3
    D: SELECT Sno FROM SC GROUP BY Sno
  • B

    举一反三

    内容

    • 0

      如果想限制sc(sno,cno,grade)表中每人最多选三门课,如何用断言表示?sc(sno,cno,grade)表示选修(学号,课程号,成绩) A: Create assertion asse1 check(3>=all( select count(*) from sc group by sno)) B: Create assertion asse1 check(3>=any( select count(*) from sc group by sno)) C: Create assertion asse1 check(3>=some( select count(*) from sc group by sno)) D: Create assertion asse1 check(3>= select count(*) from sc group by sno)

    • 1

      基于“学生-选课-课程”数据库中的三个关系: 学生表S(SNO,SNAME,SEX,BIRTHYEAR,DEPT),主码为SNO 课程表C(CNO,CNAME,TEACHER),主码为CNO 选课表SC(SNO,CNO,GRADE),主码为(SNO,CNO) [br][/br]查找“选修了至少5门课程的学生的学号”,正确的SQL语句是( )。 A: SELECT SNO FROM SC GROUP BY SNO HAVING COUNT(*) >=5; B: SELECT SNO FROM SC GROUP BY SNO WHERE COUNT(*) >=5; C: SELECT SNO FROM SC HAVING COUNT(*) >=5; D: SELECT SNO FROM SC WHERE COUNT(*) >=5;

    • 2

      如果想限制sc(sno,cno,grade)表中每人最多选三门课,如何用断言表示?sc(sno,cno,grade)表示选修(学号,课程号,成绩) A: Create assertion asse1 check(3>=all( select count(*) from sc group by sno)) B: Create assertion asse1 check(3>=any( select count(*) from sc group by sno)) C: Create assertion asse1 check(3>=some( select count(*) from sc group by sno)) D: Create assertion asse1 check(3>= select count(*) from sc group by sno)

    • 3

      查询最低成绩大于85分的学生学号和平均成绩,可以使用的查询语句是:  。 A: SELECT Sno, AVG(Grade) FROM SC HAVING MIN(Grade) > 85 GROUP BY Sno; B: SELECT Sno, AVG(Grade) FROM SC GROUP BY Sno HAVING MIN(Grade) > 85; C: SELECT Sno, AVG(Grade) FROM SC WHERE MIN(Grade) > 85 GROUP BY Sno; D: SELECT Sno, AVG(Grade) FROM SC GROUP BY Sno WHERE MIN(Grade) > 85;

    • 4

      关系SC(Sno,Cno,Grade)表示学号,课程号,成绩。现要查询平均分在90分以上的学生的学号和平均成绩,正确的语句是______。 A: SELECT Sno,AVG(Grad FROM SC WHERE AVG(Grad>=90 GROUP BY Sno B: SELECT Sno,AVG(Grad FROM SC GROUP BY Sno HAVING AVG(Grad>=90 C: SELECT Sno,AVG(Grad FROM SC WHERE AVG(Grad>=90 ORDER BY Sno D: SELECT Sno,AVG(Grad FROM SC GROUP BY Cno HAVING AVG(Grad>=90