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？