MYSQL单表查询问题求解！！

请把表结构发出来，有表结构才好写SQL语句。

1.select distinct sdept from student
2.select ssex 性别,count(*) 学生人数 from student group by ssex
3.select sno 学号, sname 姓名,sdept 系部 from student where sname like '%美'
4.select sname 姓名,year(now())-year(出生日期字段名）年龄 from student limit 3,3
5.select sno,avg(degree) from sc group by sno order by avg(degree) desc limit 1,5