帮我做下数据库编程题，谢谢

创建视图：

create view price_view as

select b.mname as 商场名,a.ino as 商品号,c.iname 商品名 as ,a.price as 价格

from sales a,market b,item c

where a.mno = b.mno and a.ino = c.ino

统计平均售价

select 商品名,avg(价格) as 平均售价 from price_view group by 商品名

1)select distinct 品牌 from 商品表2

2)select distinct 课程号 from 选课 as T ,选课 as S where T.学生号=@s1 and S.学生号=@s2 and T.课程号 = S.课程号

3）select sum(studnet_ID) from student group by major

4)select max(float) from product_table group by category

5)你自己去想想看吧，之前的我不确定自己做的是不是对的。我也是最近才在学DB

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