SQL查询语句（下），你能写对几个？-CFANZ编程社区

#查询与”刘晨“在同一个系学习的学生
SELECT Sno,Sname,Sdept FROM Student WHERE Sdept IN (SELECT Sdept FROM student WHERE Sname="刘晨");

SELECT S1.Sno,S1.Sname,S1.Sdept FROM Student S1,Student S2 WHERE S1.Sdept=S2.Sdept AND S2.Sname='刘晨';

#查询选修了课程名为“信息系统”的学生学号和姓名
SELECT Sno,Sname FROM Student WHERE Sno IN (SELECT Sno FROM SC WHERE Cno IN(
SELECT Cno FROM Course WHERE Cname='信息系统'));

SELECT Student.Sno,Sname FROM Student,SC,Course WHERE Student.Sno=SC.Sno AND SC.Cno=Course.Cno AND Course.Cname='信号系统';

#找出每个学生超过他自己选修课程平均成绩的课程号
SELECT Sno,Cno FROM SC x WHERE Grade>=(SELECT AVG(Grade) FROM SC y WHERE y.Sno=x.Sno);

#查询非计算机科学系中比计算机科学系任意一个学生年龄小的学生姓名和年龄
SELECT Sname,Sage FROM Student WHERE Sage>ANY(SELECT Sage FROM Student WHERE Sdept='CS') AND Sdept<>'CS';

SELECT Sname,Sage FROM Student WHERE Sage<(SELECT MAX(Sage) FROM Student WHERE Sdept ='CS');

#查询非计算机科学系中比计算机科学系所有学生年龄都小的学生姓名及年龄
SELECT Sname,Sage FROM Student WHERE Sage<ALL(SELECT Sage FROM Student WHERE Sdept='CS') AND Sdept<>'CS';

SELECT Sname,Sage FROM Student WHERE Sage < (SELECT MIN(Sage) FROM Student WHERE Sdept='CS') AND Sdept<>'CS';

#查询所有选修了1号课程的学生姓名
SELECT Sname FROM Student WHERE EXISTS (SELECT * FROM SC  WHERE Sno=Student.Sno AND Cno='1');

#查询没有选修1号课程的学生姓名
SELECT Sname FROM Student WHERE NOT EXISTS (SELECT * FROM SC WHERE Sno=Student.Sno AND Cno='1');