mysql语句问题

Question

select * from (select goods_id,cat_id,goods_name,shop_price from goods order by cat_id asc,shop_price desc)  tmp group by cat_id  ;

这个语句不能允许

需要

1.create table op (select goods_id,cat_id,goods_name,shop_price from goods order by cat_id asc,shop_price desc);

2.select * from op group by cat_id;

这是什么原因啊？