以下命令是相关子查询的嵌套查询是：
A: SELECT * FROM student WHERE sno IN (SELECT sno FROM sc WHERE cno = '1')
B: SELECT * FROM student WHERE EXISTS (SELECT * FROM sc WHERE cno = '1' AND sc.sno = student.sno)
C: SELECT sno, cno FROM sc x WHERE grade>(SELECT AVG(grade) FROM sc y WHERE y.sno = x.sno)
D: 以上都是
A: SELECT * FROM student WHERE sno IN (SELECT sno FROM sc WHERE cno = '1')
B: SELECT * FROM student WHERE EXISTS (SELECT * FROM sc WHERE cno = '1' AND sc.sno = student.sno)
C: SELECT sno, cno FROM sc x WHERE grade>(SELECT AVG(grade) FROM sc y WHERE y.sno = x.sno)
D: 以上都是
举一反三
- 下列查询中,属于相关子查询的有（）。 A: SELECT * FROM student WHERE sno IN (SELECT sno FROM sc WHERE cno='1'); B: SELECT sno, cno FROM SC x WEHRE grade>=(SELECT AVG(grade) FROM SC y WHERE y.sno = x.sno); C: SELECT sname FROM student WHERE EXISTS(SELECT * FROM sc WHERE sno=student.sno AND cno='1'); D: SELECT sname FROM student WHERE NOT EXISTS(SELECT * FROM course WHERE NOT EXISTS(SELECT * FROM sc WHERE sc.sno=student.sno AND sc.cno=course.cno));
- “查询没有学习成绩的学生的学号和课程号”的SQL语 句是( ) (2.0) 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 = ' '
- 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’);
- 查询所有有成绩的学生学号和课程号。正确的SELECT语句是（）。 A: Select sno , cno from sc where grade < > null B: Select sno as 学号, cno as 课程号 from sc where grade is not null C: Select sno , cno from sc where grade !=‘ ’ D: Select sno , cno from sc where grade is not null
- 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);