(1)select CNAME,TEACHER from 课程 where TEACHER='LIU'
(2)select S#,SNAME form 学生 where age>23
(3)select SNAME from 学生,学习,课程 where 学生.S#=学习.S# and 学习.C#=课程.C# and SEX='女'
(4)select C# from 学习SC,学生S where SNAME LIKE 'WANG%' and C# not in(select C# from 课程C)
(5)select S# from S where 2<=(select count(*) from SC whre SC.S#=S.S#)
第六个不太会
(7)select S# from SC where C# in(select C# from C where teacher='刘%')