MySQL的內部聯接造成乘法

Question

基本上我有這樣的結構：

• 交易屬於多個頻道
• 新政有許多DealSales
• 新政屬於通道

時，我想找到一筆交易銷售的金額，我用這個查詢：

SELECT targets.id,SUM(deal_sales.amount_sold) AS amount_sold 
FROM deal_sales 
INNER JOIN deals ON deals.id = deal_sales.deal_id 
INNER JOIN targets ON deals.target_id = targets.id 
WHERE targets.approved = 1 AND targets.active = 1 
GROUP BY targets.id 

它工作得很好，問題是當我需要通過渠道來進行篩選，找到一個交易的渠道銷售金額：

SELECT targets.id,SUM(deal_sales.amount_sold) AS amount_sold 
FROM 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** 
WHERE targets.approved = 1 AND targets.active = 1 
GROUP BY targets.id 

當我添加了加盟渠道表格中，AMOUNT_SOLD是乘以交易與每個渠道的關係。我怎樣才能避免這種情況？

Answer 1

或者用已存在

例如

SELECT targets.id,SUM(deal_sales.amount_sold) AS amount_sold 
FROM deal_sales 
INNER JOIN deals ON deals.id = deal_sales.deal_id 
INNER JOIN targets ON deals.target_id = targets.id 

WHERE targets.approved = 1 AND targets.active = 1 
    and 
    deals.id IN (SELECT deal_id from channels_deals where something = 1) 
GROUP BY targets.id 

Answer 2

Try this: 

SELECT channels_deals.deal_id,SUM(deal_sales.amount_sold) AS amount_sold 
FROM 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 
WHERE targets.approved = 1 AND targets.active = 1 
GROUP BY channels_deals.deal_id