hi to all,
i have a problem i want join three tables, this is the structure (semplified)

Seller
IdSeller
NameSeller

BuyFromSeller
IdBuy
Qty
Cost
FkSeller

Sell
IdSell
QtySell
Price
FkSeller

i want know all the buy and the sell for seller (if there are)

i have tried
select
Seller.NameSeller,
sum(buyfromseller.qty*buyfromseller.cost) as buys,
sum(sell.qtysell*sell.price) as Sells,
from
Seller
left join buyfromseller on buyfromseller.fkseller=seller.idseller
left join sell on sell.fkseller=seller.idseller
group by
seller.nameseller

but it turn me doubles values for the sell sum, how can i resolve it?

thanks in advance.