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--设有三个关系--S（S#,SNAME,AGE,SEX)--SC(S#,C#,GRADE)--C(C#,CNAME,TEACHER)--（1）检索LIU老师所授课程的课程号、课程名select c#,cname from cwhere teacher='LIU'--（2）检索年龄大于23岁的男同学的学号和姓名select s#,sname from swhere age>23 and sex='男'--（3）检索学号为S3学生所学课程的课程名与任课教师名select cname,teacher from c,scwhere c.c#=sc.c# and s#='s3'--（4）检索至少选修LIU老师所授课程中一门课程的女学生的姓名--1.嵌套查询select sname from swhere sex='女' and s# in(select s# from sc where c# in(select c# from c where teacher='LIU'))--2.多表联合查询select sname from s,sc,c where s.s#=sc.s# and sc.c#=c.c# and teacher='LIU' and s.sex='女'--（5）检索王同学不学的课程号--1.select c# from c where c# not in(select c# from sc where s# in (select s# from s where sname='wang'))--2.select c# from sc where c# not in(select c# from s,sc where s.s#=sc.s# and sname='wang') --（6）检索至少选修两门课程的学生学号select distinct x.s# from sc x,sc ywhere x.s#=y.s# and x.c#!=y.c#--（7）检索全部学生都选修的课程的课程号与课程名--1.select c.c#,cnamefrom sc,cwhere sc.c#=c.c#group by c.c#,cname having COUNT(*)=(select COUNT(*)from s)--2.select c#,cname from cwhere not exists(select * from swhere s# not in(select * from sc where sc.c#=c.c#));--（8）检索选修课程包含LIU老师所授课程的学生学号select distinct s# from scwhere c# in(select c# from cwhere teacher='liu');

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