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));
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));
举一反三
- 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
- 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);
- 下列SQL语句中，_________可以在“学生-课程”数据库正确实现“查询所有选修了1号课程的学生姓名”。 A: SELECT SnameFROM Student, SCWHERE SC.Cno= '1' B: SELECT SnameFROM Student, SCWHERE Student.Sno=SC.Sno AND SC.Cno= 1 C: SELECT Sname FROM Student WHERE Sno= (SELECT Sno FROM SC WHERE Cno= '1') D: SELECT Sname FROM Student WHERE EXISTS (SELECT * FROM SC WHERE Sno=Student.Sno AND Cno= '1')
- 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
- 查询每个学生的学号、姓名、选修的课程名及成绩，下列（)的操作是正确的。 A: select student,sno,sname,grade from student,sc where student.sno=sc.sno and sc.cno=course.cno B: select student,sno,sname,grade from student,sc,cource where student.sno=sc.sno C: select student,sno,sname,grade from student,sc,cource where sc.cno=course.cno D: select student,sno,sname,grade from student,sc,cource where student.sno=sc.sno and sc.cno=course.cno