举一反三
- 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);
- 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
- 下列SQL语句中，_____________可以在“学生-课程”数据库正确实现“查询选修2号课程且成绩在90分以上的所有学生的学号和姓名”。 A: SELECT Sno, Sname FROM Student, SC WHERE Student.Sno = SC.Sno ANDSC.Cno= ‘2’ AND SC.Grade > 90 B: SELECT Student.Sno, Sname FROM Student, SC WHERE Student.Sno = SC.Sno ANDSC.Cno=‘2’AND SC.Grade > 90 C: SELECT Sno, Sname FROM Student, SC WHERE SC.Cno=‘2’AND SC.Grade > 90 D: SELECT Student.Sno, Sname FROM Student, SC WHERE Student.Sno = SC.Sno AND SC.Grade > 90
- 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));
- 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
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【多选题】针对学生选课数据库S_T，以下()操作实现了student表与sc之间的自然连接。 A. select student.* , cno, grade from student join sc on student.sno=sc.sno B. select student.* , sc.* from student , sc where student.sno=sc.sno C. select student.sno, sname, ssex, sage, sdept , cno, grade from student , sc where student.sno=sc.sno D. select student.* , cno, grade from student , sc where student.sno=sc.sno
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现有学生表S、课程表C和学生选课表SC，它们的结构如下：[br][/br] S（S＃, SN, SEX, AGE, DEPT） C（C＃, CN，TEACHER） SC（S＃, C＃, GRADE） 其中：S＃为学号，SN为姓名，SEX为性别，AGE为年龄，DEPT为系别，C＃为课程号，CN为课程名，GRADE为成绩。 要查找分数高于90分的学生的学号和姓名的语句为（ ） A: select student.sno，sname from student,sc where student.sno=sc.sno and grade>90 B: select student.sno,sname from student,sc where grade>90 C: select sno，sname from sc where grade>90 D: select sno，grade from student where grade>90
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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')
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查询所有成绩均大于80分的学生姓名,应执行( )语句 A: SELECT SNAME FROM STUDENT WHERE EXISTS (SELECT *FROM SC WHERE STUDENSNO = SC.SNO AND GRADE> 80); B: SELECT SNAME FROM STUDENT WHERE EXISTS (SELECT *FROM SC WHERE STUDENSNO = SC.SNO AND GRADE C: SELECT SNAME FROM STUDENT WHERE NOT EXISTS (SELECT *FROM SC WHERE STUDENSNO = SC.SNO AND GRADE D: SELECT SNAME FROM STUDENT WHERE NOT EXISTS (SELECT *FROM SC WHERE STUDENSNO = SC.SNO AND GRADE> 80);
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查询所有学生的选课信息，结果包括学号，姓名，性别，年龄，选课课程名，成绩 select ,sname,sex,sage,cname,grade from student,course,sc where student.sno=sc.sno and ;