1. 创建学生表 S(命名格式“姓名拼音_三位学号_s”，如 LBJ_023_s)并插入数据

2. 创建课程表 C(命名格式“姓名拼音_三位学号_c”，如 LBJ_023_c) 并插入数据

select * s.Sname, c.Cname, sc.Grade from LYL_116_s s, LYL_116_c c, LYL_116_sc scwhere s.S# = sc.S# and c.C# = sc.C#

select cs.Sname'名字', avg(cs.Grade)'平均成绩'
from (select s.Sname, c.Cname, sc.Gradefrom LYL_116_s s, LYL_116_c, LYL_116_scwhere s.S# = sc.S# and c.C# = sc.C#) cs group by cs.Sname

select c.C#, sc.Grade from LYL_116_c c, LYL_116_sc sc
where c.C# = sc.C# and c.C# = 'C5'

select sc.S#, S.Sname from(select sc.S# from (select C# from LYL_116_c where Cname = '九阴真经')s, LYL_116_sc sc where s.C# = sc.C#) cs, LYL_116_s s 
where cs.S# = s.S#

select sc.S# from LYL_116_sc sc where sc.C# = 'C1' or sc.C# = 'C5'

select LYL_116_s.S# from LYL_116_s where S# IN(select S# from(select S# from LYL_116_sc where LYL_116_sc.C#='C1' union allselect S# from LYL_116_sc where LYL_116_sc.C#='C8') group by S# having COUNT(*)=2)

select s.Sname, s.Sage from LYL_116_s s,(select sc.S# from LYL_116_sc sc where sc.C#='C8') cswhere s.S# != cs.S#