表person(personID,name,adress)
表goods(goodsID,cost,sign)
表trade(personID,goodsID)
------------------------------
不知道sign是干什么的?
表goods(goodsID,cost,sign)
表trade(personID,goodsID)
------------------------------
不知道sign是干什么的?
group by personID
from person p,goods g,trade t
where g.goodsID = t.goodsID
and p.personID = t.personID
group by name;
where a.id=c.person_id and b.id=c.commodity_id group by a.name