ruby on rails - mysql inner join causing multiplication -

basically have structure:

• deal has , belongs many channels
• deal has many dealsales
• deal belongs channel

when want find amount sold deal, use query:

select targets.id,sum(deal_sales.amount_sold) amount_sold deal_sales  inner join deals on deals.id = deal_sales.deal_id  inner join targets on deals.target_id = targets.id  targets.approved = 1 , targets.active = 1 group targets.id 

its working fine, problem when need filter channel, find amount sold deal in channel:

select targets.id,sum(deal_sales.amount_sold) amount_sold deal_sales  inner join deals on deals.id = deal_sales.deal_id  inner join targets on deals.target_id = targets.id  **inner join channels_deals on channels_deals.deal_id = deals.id** targets.approved = 1 , targets.active = 1 group targets.id 

when add join channels table, amount_sold multiplied each channel deal has relation with. how can avoid this?

use in or exists

for example

select targets.id,sum(deal_sales.amount_sold) amount_sold deal_sales  inner join deals on deals.id = deal_sales.deal_id  inner join targets on deals.target_id = targets.id   targets.approved = 1 , targets.active = 1   ,     deals.id in (select deal_id channels_deals = 1) group targets.id